CHAPTER
11
Alterations in
Nutritional Status
Joan Pleuss
NUTRITIONAL STATUS
Energy Metabolism
Adipose Tissue
Anabolism and Catabolism
Glucose Metabolism
Fat Metabolism
Protein Metabolism
Energy Expenditure
Basal Metabolic Rate
Diet- and Exercise-Induced Thermogenesis
Recommended Dietary Allowances and
Dietary Reference Intakes
Nutritional Needs
Calories
Proteins
Fats
Carbohydrates
Vitamins
Minerals
Fiber
Nutritional Assessment
Diet Assessment
Health Assessment
Anthropometric Measurements
Laboratory Studies
OVERNUTRITION AND OBESITY
Causes of Obesity
Upper and Lower Body Obesity
Health Risks Associated With Obesity
Prevention of Obesity
Treatment of Obesity
Dietary Therapy
Physical Activity
Behavior Therapy
Pharmacotherapy
Weight Loss Surgery
Childhood Obesity
UNDERNUTRITION
Malnutrition and Starvation
Protein-Calorie Malnutrition
Diagnosis
Treatment
Eating Disorders
Anorexia Nervosa
Bulimia Nervosa and Binge Eating
“
Y
ou are what you eat” is a familiar maxim. To a great
extent, nutrition determines how a person looks,
feels, and acts. The need for adequate nutrition begins at the time of conception and continues throughout
life. Nutrition provided by food or supplements in the
proper proportions enables the body to maintain life, to
grow physically and intellectually, to heal and repair tissue, and to maintain the stamina necessary for well-being.
This chapter addresses nutritional status, overnutrition
and obesity, and undernutrition.
Nutritional Status
After completing this section of the chapter, you should be able to
meet the following objectives:
✦ Define nutritional status
✦ Define calorie and state the number of calories derived
from the oxidation of 1 g of protein, fat, or carbohydrate
✦ Explain the difference between anabolism and catabolism
✦ Relate the processes of glycogenolysis and gluconeogenesis to the regulation of blood glucose by the liver
✦ Define basal metabolic rate and cite factors that affect it
✦ State the purpose of the Recommended Dietary
Allowance of calories, proteins, fats, carbohydrates,
vitamins, and minerals
✦ Describe methods used for a nutritional assessment
✦ State the factors used in determining body mass index
and explain its use in evaluating body weight in terms
of undernutrition and overnutrition
217
218
UNIT III
Integrative Body Functions
Nutritional status describes the condition of the body
related to the availability and use of nutrients. Nutrients
are derived from the digestive tract through the ingestion
of foods or, in some cases, through liquid feedings that are
delivered directly into the gastrointestinal tract by a synthetic tube (i.e., tube feedings). The exception occurs in
persons with certain illnesses in which the digestive tract
is bypassed and the nutrients are infused directly into the
circulatory system. Once inside the body, nutrients are
used for energy or as the building blocks for tissue growth
and repair. When excess nutrients are available, they frequently are stored for future use. If the required nutrients
are unavailable, the body adapts by conserving and using
its nutrient stores.
ENERGY METABOLISM
Energy is measured in heat units called calories. A calorie,
spelled with a small c and also called a gram calorie, is the
amount of heat or energy required to raise the temperature
of 1 g of water by 1°C. A kilocalorie (kcal), or large calorie, is
the amount of energy needed to raise the temperature of
1 kg of water by 1°C.1 Because a calorie is so small, kilocalories often are used in nutritional and physiologic studies.
The oxidation of proteins provides 4 kcal/g; fats, 9 kcal/g;
carbohydrates, 4 kcal/g; and alcohol, 7 kcal/g.
All body activities require energy, whether they involve an individual cell, a single organ, or the entire body.
Metabolism is the organized process through which nutrients such as carbohydrates, fats, and proteins are broken
down, transformed, or otherwise converted into cellular
energy. The process of metabolism is unique in that it enables the continual release of energy, and it couples this energy with physiologic functioning. For example, the energy
used for muscle contraction is derived largely from energy
sources that are stored in muscle cells and then released as
the muscle contracts. Because most of our energy sources
ENERGY METABOLISM
➤ All body activities require energy, whether they involve a
single cell, a single organ, or the entire body.
➤ Energy, which is measured in kilocalories (kcal), is obtained
from foods.
➤ Fats, which are a concentrated water-free energy source,
contain 9 kcal/g. They are stored in fat cells as triglycerides, which are the main storage sites for energy.
➤ Carbohydrates are hydrated fuels, which supply 4 kcal/g.
They are stored in limited quantities as glycogen and can
be converted to fatty acids and stored in fat cells as
triglycerides.
➤ Amino acids, which supply 4 kcal/g, are used in building
body proteins. Amino acids in excess of those needed for
protein synthesis are converted to fatty acids, ketones, or
glucose and are stored or used as metabolic fuel.
come from the nutrients in the food that is eaten, the ability to store energy and control its release is important.
Adipose Tissue
More than 90% of body energy is stored in the adipose tissues of the body. Adipocytes, or fat cells, occur singly or in
small groups in loose connective tissue. In many parts of
the body, they cushion body organs such as the kidneys. In
addition to isolated groups of fat cells, entire regions of fat
tissue are committed to fat storage. Collectively, fat cells
constitute a large body organ that is metabolically active in
the uptake, synthesis, storage, and mobilization of lipids,
which are the main source of fuel storage for the body. Some
tissues, such as liver cells, are able to store small amounts of
lipids, but when these lipids accumulate, they begin to interfere with cell function. Adipose tissue not only serves as
a storage site for body fuels but also provides insulation for
the body, fills body crevices, and protects body organs.
Studies of adipocytes in the laboratory have shown that
fully differentiated cells do not divide. However, such cells
have a long life span, and anyone born with large numbers
of adipocytes runs the risk of becoming obese. Some immature adipocytes capable of division are present in postnatal
life; these cells respond to estrogen stimulation and are the
potential source of additional fat cells during postnatal life.1
Fat deposition results from proliferation of these existing
immature adipocytes and can occur as a consequence of excessive caloric intake when a woman is breast-feeding or
during estrogen stimulation around the time of puberty. An
increase in fat cells also may occur during late adolescence
and in middle-aged persons who already are overweight.
There are two types of adipose tissue: white fat and
brown fat. White fat, which despite its name is cream colored or yellow, is the prevalent form of adipose tissue in
postnatal life. It constitutes 10% to 20% of body weight in
adult males and 15% to 25% in adult females. At body
temperature, the lipid content of fat cells exists as an oil.
It consists of triglycerides, which are made up of three molecules of fatty acids esterified to a glycerol molecule. Triglycerides, which contain no water, have the highest caloric
content of all nutrients and are an efficient form of energy
storage. Fat cells synthesize triglycerides from dietary fats
and carbohydrates. Insulin is required for transport of
glucose into fat cells. When calorie intake is restricted for
any reason, fat cell triglycerides are broken down, and the
resultant fatty acids and glycerol are released as energy
sources.
Brown fat differs from white fat in terms of its thermogenic capacity or ability to produce heat. Brown fat, the
site of diet-induced thermogenesis and nonshivering thermogenesis, is found primarily in early neonatal life in humans and in animals that hibernate. In humans, brown fat
decreases with age but is still detectable in the sixth decade. This small amount of brown fat has a minimal effect
on energy expenditure.
Anabolism and Catabolism
There are two phases of metabolism: anabolism and catabolism. Anabolism is the phase of metabolic storage and
synthesis of cell constituents. Anabolism does not provide
CHAPTER 11
energy for the body; it requires energy. Catabolism involves
the breakdown of complex molecules into substances that
can be used in the production of energy. The chemical intermediates for anabolism and catabolism are called metabolites (e.g., lactic acid is a metabolite formed when glucose
is broken down in the absence of oxygen). Both anabolism
and catabolism are catalyzed by enzyme systems located
in body cells. A substrate is a substance on which an enzyme acts. Enzyme systems selectively transform fuel substrates into cellular energy and facilitate the use of energy
in the process of assembling molecules to form energy
substrates and storage forms of energy.
Because body energy cannot be stored as heat, the
cellular oxidative processes that release energy are lowtemperature reactions that convert food components to
chemical energy that can be stored. The body transforms
carbohydrates, fats, and proteins into the intermediary compound, adenosine triphosphate (ATP). ATP is called the energy
currency of the cell because almost all body cells store and use
ATP as their energy source (see Chapter 4). The metabolic
events involved in ATP formation allow cellular energy to
be stored, used, and replenished.
Glucose Metabolism
Glucose is a six-carbon molecule; it is an efficient fuel that,
when metabolized in the presence of oxygen, breaks down
to form carbon dioxide and water (Fig. 11-1). Although
many tissues and organ systems are able to use other forms
of fuel, such as fatty acids and ketones, the brain and nervous system rely almost exclusively on glucose as a fuel
source. The nervous system can neither store nor synthesize glucose; instead, it relies on the minute-by-minute
extraction of glucose from the blood to meet its energy
needs. In the fed and early fasting state, the nervous system requires approximately 100 to 115 g of glucose per day
to meet its metabolic needs.
The liver regulates the entry of glucose into the blood.
Glucose ingested in the diet is transported from the gastrointestinal tract, through the portal vein, and to the liver before it gains access to the circulatory system (Fig. 11-2). The
liver stores and synthesizes glucose. When blood sugar is increased, the liver removes glucose from the blood and stores
it for future use. Conversely, the liver releases its glucose
stores when blood sugar drops. In this way, the liver acts as
a buffer system to regulate blood sugar levels. Blood sugar
levels usually reflect the difference between the amount of
glucose released into the circulation by the liver and the
amount of glucose removed from the blood by body cells.
Excess glucose is stored in two forms. It can be converted to fatty acids and stored in fat cells as triglycerides, or
it can be stored in the liver and skeletal muscle as glycogen
(see Fig. 11-2). Small amounts of glycogen also are stored in
the skin and in some of the glandular tissues.
Glycogenolysis. Glycogenolysis, or the breakdown of glycogen, is controlled by the action of two hormones: glucagon and epinephrine. Epinephrine is more effective in
stimulating glycogen breakdown in muscle, whereas the
liver is more responsive to glucagon. The synthesis and
degradation of glycogen are important because they help
maintain blood sugar levels during periods of fasting and
219
Alterations in Nutritional Status
H
H
C
OH
H
C
OH
H
C
OH
HO
C
H
H
C
OH
H
C
O
Glucose
(straight chain)
O
CH
O
R2
C
O
O
C
CH2
C
R1
O
O
C
R3
Triglyceride
H
R
C
COOH
NH2
Amino acid
FIGURE 11-1 Glucose, triglyceride, and amino acid structure.
strenuous exercise. Only the liver is able to release its glucose
stores into the blood for use by other tissues, such as the
brain and nervous system. Glycogen breaks down to form a
phosphorylated glucose molecule, and in this form, it is too
large to pass through the cell membrane. The liver, but not
skeletal muscle, has the enzyme glucose-6-phosphatase,
which is needed to remove the phosphate group and allow
the glucose molecule to enter the bloodstream.
Gluconeogenesis. The synthesis of glucose is referred to as
gluconeogenesis, or the building of glucose from new sources.
The process of gluconeogenesis, most of which occurs in
the liver, converts amino acids, lactate, and glycerol into
glucose. Although many cells use fatty acids as a fuel source,
they cannot be converted to glucose.
Glucose produced through the process of gluconeogenesis is either stored in the liver as glycogen or released into
the general circulation. During periods of food deprivation
or when the diet is low in carbohydrates, gluconeogenesis
provides the glucose that is needed to meet the metabolic
needs of the brain and other glucose-dependent tissues.
Several hormones stimulate gluconeogenesis, including
220
UNIT III
Integrative Body Functions
Required energy source for brain
and nerve metabolism
Skeletal
muscle
Central nervous
system
Released into
the blood
Stored as
muscle glycogen
Stored as triglycerides
in fat cells
Adipose
tissue
Liver
Stored as glycogen or
synthesized through
gluconeogenesis
Small
intestine
Transported in the
portal circulation
Glucose absorption
from the gut
FIGURE 11-2 Regulation of blood glucose by the liver.
glucagon, glucocorticoid hormones from the adrenal cortex, and thyroid hormone.
Fat Metabolism
The average American diet provides approximately 33% of
calories in the form of fats. In contrast to glucose, which
yields only 4 kcal/g, each gram of fat yields 9 kcal. Another
30% to 50% of the carbohydrates consumed in the diet are
converted to triglycerides for storage.
A triglyceride contains three fatty acids linked by a
glycerol molecule (see Fig. 11-1). Fatty acids and triglycerides can be derived from dietary sources, they can be
synthesized in the body, or they can be mobilized from fat
depots. Excess carbohydrates are converted to triglycerides
and transported to adipose cells for storage. One gram of
anhydrous (water-free) fat stores more than six times as
much energy as 1 hydrated gram of glycogen. One reason
weight loss is greatest at the beginning of a fast or weight
loss program is that this is when the body uses its watercontaining glycogen stores. Later, when the body begins
to use energy stored as triglycerides, water losses are decreased, and weight loss tends to plateau.
The mobilization of fatty acids for use in energy production is facilitated by the action of lipases (i.e., enzymes) that break the triglycerides into three fatty acids
and a glycerol molecule. The activation of lipases and subsequent mobilization of fatty acids is stimulated by epinephrine, glucocorticoid hormones, growth hormones, and
glucagon. After triglycerides have been broken down, their
fatty acids and glycerol enter the circulation and travel to
the liver, where they are removed from the blood and used
as a source of energy or converted to ketones.
The efficient burning of fatty acids requires a balance
between carbohydrate and fat metabolism. The ratio of
fatty acid and carbohydrate use is altered in situations
that favor fat breakdown, such as diabetes mellitus and
fasting. In these situations, the liver produces more ketones than it can use; this excess is released into the bloodstream. Ketones can be an important source of energy
because even the brain adapts to the use of ketones during prolonged periods of starvation. A problem arises,
however, when fat breakdown is accelerated and the production of ketones exceeds tissue use. Because ketones
are organic acids, they cause ketoacidosis when they are
present in excessive amounts.
Protein Metabolism
Approximately three fourths of body solids are proteins.
Proteins are essential for the formation of all body structures, including genes, enzymes, contractile structures in
muscle, matrix of bone, and hemoglobin of red blood cells.
Amino acids are the building blocks of proteins.
Twenty amino acids are present in body proteins in significant quantities. Each amino acid has an acidic group
(COOH) and an amino group (NH2; see Fig. 11-1). Unlike
glucose and fatty acids, there is only a limited facility for
the storage of excess amino acids in the body. Most of the
stored amino acids are contained in body proteins. Amino
acids in excess of those needed for protein synthesis are
converted to fatty acids, ketones, or glucose and are stored
or used as metabolic fuel. Because fatty acids cannot be
converted to glucose, the body must break down proteins
and use the amino acids to generate glucose during periods when metabolic needs exceed food intake. The liver
has the enzymes and mechanisms needed to deaminate
and to convert the amino groups from the amino acid to
urea. The breakdown or degradation of proteins and
amino acids occurs primarily in the liver, which also is the
site of gluconeogenesis.
ENERGY EXPENDITURE
The expenditure of body energy results from four mechanisms of heat production (i.e., thermogenesis): basal
metabolic rate or resting energy equivalent, diet-induced
thermogenesis, exercise-induced thermogenesis, and thermogenesis in response to changes in environmental conditions. The amount of energy used varies with age, body
size, rate of growth, and state of health.
Basal Metabolic Rate
The basal metabolic rate (BMR) refers to the chemical reactions occurring when the body is at rest. These reactions
are necessary to provide energy for maintenance of normal
body temperature, cardiovascular and respiratory function, muscle tone, and other essential activities of tissues
and cells in the resting body. The resting metabolic rate
constitutes 50% to 70% of body energy needs.1 The BMR
is measured using an instrument called a metabolator that
measures the rate of oxygen use by a person. Oxygen con-
CHAPTER 11
sumption is measured under basal conditions: after a full
night’s sleep, after at least 12 hours without food, and
while the person is awake and at rest in a warm and comfortable room. The BMR is then calculated in terms of calories per hour and normally averages approximately 65 to
70 calories per hour in an average 70-kg man.1 Women in
general have a 5% to 10% lower BMR than men because of
their higher percentage of adipose tissue. Although much
of the BMR is accounted for by essential activities of the
central nervous system, kidneys, and other body organs,
the variations in BMR among different individuals are related largely to skeletal muscle mass and body size. Under
normal resting conditions, skeletal muscle accounts for
20% to 30% of the BMR.1 For this reason, the BMR is commonly corrected for body size by expressing it as calories
per hour per square meter of body surface area. Factors
that affect the BMR are age, sex, physical state, and pregnancy. A progressive decline in the normal BMR occurs
with aging1 (Fig. 11-3). The BMR can be used to predict the
calorie needs for maintenance of nutrition.
The resting energy equivalent (REE) is used for predicting
energy expenditure. Several equations that determine REE
have been published. Although the Harris-Benedict equation has been the most widely used, research indicates that
the World Health Organization equation has better predicting value2 (Table 11-1). Multiplying the REE by a factor
of 1.2 usually adequately predicts the caloric needs for
maintenance of nutrition during health. A factor of 1.5 usually provides the needed nutrients during repletion and
during illnesses such as pneumonia, long bone fractures,
cancer, peritonitis, and recovery from most types of surgery.
Diet- and Exercise-Induced Thermogenesis
Diet-induced thermogenesis, or thermic effect of food, describes the energy used by the body for the digestion, absorption, and assimilation of food after its ingestion. It is
Estimated Energy Requirements (EER)
for Men and Women 30 Years of Age
With a Body Mass Index of 18.5
TABLE 11-1
Height
(m [in])
1.50
(59)
1.65
(65)
1.80
(71)
221
Alterations in Nutritional Status
PAL*
Sedentary
Low active
Active
Very active
Sedentary
Low active
Active
Very active
Sedentary
Low active
Active
Very active
Weight
(kg[lb])
EER†, men
(kcal/d)
EER†, women
(kcal/d)
41.6
(92)
1.848
2.009
2.215
2.554
2.068
2.254
2.490
2.880
2.301
2.513
2.782
3.225
1.625
1.803
2.025
2.291
1.816
2.016
2.267
2.567
2.015
2.239
2.519
2.855
50.4
(111)
59.9
(132)
NOTE: For each year below 30 years of age, add 7 kcal/d for women and
10 kcal/d for men. For each year above 30 years of age, subtract 7 kcal/
day for women and 10 kcal/d for men.
*PAL = total energy expenditure + basal energy expenditure,
PA = 1.0 if PAL ≥1.0 <1.4 (sedentary)
PA = 1.12 if PAL ≥1.4 <1.6 (low activity)
PA = 1.27 if PAL ≥1.6 <1.9 (active)
PA = 1.45 if PAL ≥1.9 <2.5 (very active)
† EER derived from the following regression equations based on doubly
labeled water data:
Adult man = 661.8 − 9.53 × age (y) × PA ×
(15.91 × wt [kg] + 539.6 × ht [m])
Adult woman = 354.1 − 6.91 × age (y) × PA × (9.36 × wt [kg] + 726 ×
ht [m]), where PA refers to coefficient for physical activity levels (PAL).
Adapted from Dietary reference intakes for energy carbohydrate, fiber,
fat, fatty acids, cholesterol, protein, and amino acids (2002). This report
may be accessed on-line via www.nap.edu. Copyright © 2002 by the
National Academy of Sciences. All rights reserved.
energy expended over and above the caloric value of the
food and accounts for approximately 10% of the total
calories expended. When food is eaten, the metabolic rate
rises and then returns to normal within a few hours. The
amount of energy expended for physical activity is determined by the type of activity performed, the length of participation, and the person’s weight and physical fitness.
RECOMMENDED DIETARY ALLOWANCES
AND DIETARY REFERENCE INTAKES
FIGURE 11-3 Normal basal metabolic rates at different ages for each
sex. (Guyton A.C., Hall J.E. [1996]. Medical physiology [9th ed., p. 909].
Philadelphia: W.B. Saunders)
The Recommended Dietary Allowances (RDAs) define the intakes that meet the nutrient needs of almost all healthy
persons in a specific age and sex group.3 The RDAs, which
are periodically updated, have been published since 1941
by the National Academy of Sciences. The RDA is used in
advising persons about the level of nutrient intake they
need to decrease the risk of chronic disease.
The Dietary Reference Intake (DRI) includes a set of at
least four nutrient-based reference values: the RDA, the
Adequate Intake, the Estimated Average Requirement,
and the Tolerable Upper Intake Level, each of which has
specific uses.4 The Adequate Intake (AI) is set when there
is not enough scientific evidence to estimate an average
222
UNIT III
Integrative Body Functions
requirement. The AI is derived from experimental or observational data that show a mean intake that appears to
sustain a desired indicator of health. An Estimated Average
Requirement is the intake that meets the estimated nutrient
need of half of the persons in a specific group. This estimate is used as the basis for developing the RDA and is
expected to be used by nutrition policy makers in the evaluation of the adequacy of a nutrient for a specific group and
for planning how much of the nutrient the group should
consume. The Tolerable Upper Intake Level is the maximum
intake that is judged unlikely to pose a health risk in almost
all healthy persons in a specified group. It refers to the
total intakes from food, fortified food, and nutrient supplements. This value is not intended to be a recommended
level of intake, and there is no established benefit for persons who consume nutrients at the RDA or AI levels.
The DRIs are regularly reviewed and updated by the
Food and Nutrition Board of the Institute of Medicine and
the National Academy of Sciences. The current recommended DRIs for selected vitamins and minerals that
have been released between 1997 and 2001 are listed in
Tables 11-2 and 11-3. In 2002, RDAs were established for
dietary carbohydrate and protein. An AI was set for total
fiber and linoleic and α-linolenic acids. The Food and Nutrition Board also established Acceptable Macronutrient
Distribution Ranges (AMDR) as a percentage of energy intake for fat, carbohydrate, linoleic and α-linolenic acids,
and protein5 (Table 11-4).
Food and supplement labels use Daily Values (DVs),
which are set by the U.S. Food and Drug Administration
(FDA). However, the DVs are based on data that is older
than the data used to determine the DRIs. Percent Daily
Value (% DV) tells the consumer what percentage of the DV
one serving of a food or supplement supplies.
Proteins, fats, carbohydrates, vitamins, and minerals
each have their own function in providing the body with
what it needs to maintain life and health. Recommended
allowances have not been established for every nutrient;
some are given as a safe and adequate intake, but others,
such as carbohydrates and fats, are expressed as a percentage of the calorie intake.
NUTRITIONAL NEEDS
Calories
Energy requirements are greater during growth periods.
Infants require approximately 115 kcal/kg at birth,
105 kcal/kg at 1 year, and 80 kcal/kg of body weight between 1 to 10 years of age. During adolescence, boys require 45 kcal/kg of body weight and girls require 38 kcal/kg
of body weight. During pregnancy, a woman needs an
extra 300 kcal/day above her usual requirement, and during the first 3 months of breast-feeding, she requires an additional 500 kcal.3 Table 11-5 can be used to predict the
caloric requirements of healthy adults.5
posed of amino acids, nine of which are essential to the
body. These are leucine, isoleucine, methionine, phenylalanine, threonine, tryptophan, valine, lysine, and histidine. The foods that provide these essential amino acids in
adequate amounts are milk, eggs, meat, fish, and poultry.
Dried peas and beans, nuts, seeds, and grains contain all
the essential amino acids but in less than adequate proportions. These proteins need to be combined with each
other or with complete proteins to meet the amino acid requirements for protein synthesis. Diets that are inadequate
in protein can result in kwashiorkor. If calories and protein are inadequate, protein-calorie malnutrition occurs.
Unlike carbohydrates and fats, which are composed of
hydrogen, carbon, and oxygen, proteins contain 16% nitrogen; therefore, nitrogen excretion is an indicator of protein intake. If the amount of nitrogen taken in by way of
protein is equivalent to the nitrogen excreted, the person is
said to be in nitrogen balance. A person is in positive nitrogen balance when the nitrogen consumed by way of protein is greater than the amount excreted. This occurs during
growth, pregnancy, or healing after surgery or injury. A negative nitrogen balance often occurs with fever, illness, infection, trauma, or burns, when more nitrogen is excreted
than is consumed. It represents a state of tissue breakdown.
Fats
Dietary fats are composed primarily of triglycerides (i.e., a
mixture of fatty acids and glycerol). The fatty acids are saturated (i.e., no double bonds), monounsaturated (i.e., one
double bond), or polyunsaturated (i.e., two or more double bonds). The saturated fatty acids elevate blood cholesterol, whereas the monounsaturated and polyunsaturated
fats lower blood cholesterol. Saturated fats usually are
from animal sources and remain solid at room temperature. With the exception of coconut and palm oils (which
are saturated), unsaturated fats are found in plant oils and
usually are liquid at room temperature. Dietary fats provide energy, function as carriers for the fat-soluble vitamins, serve as precursors of prostaglandins, and are a source
of fatty acids. The polyunsaturated fatty acid linoleic acid
is the only fatty acid that is required. A deficiency of linoleic acid results in dermatitis. An Adequate Intake (AI)
has been set for both linoleic and α-linolenic acids5 (see
Table 11-4). Because vegetable oils are rich sources of linoleic acid, this level can be met by including two teaspoons
per day of vegetable oil in the diet.
Fat is the most concentrated source of energy. The Food
and Nutrition Board has set an Acceptable Macronutrient
Distribution Range (AMDR) for fat of no less than 20% to
prevent the fall of high-density lipoprotein (HDL) cholesterol associated with very-low-fat diets.5 Guidelines from the
National Cholesterol Education Program recommend that
25% to 35% of the calories in the diet should come from
fats.6 Cholesterol is the major constituent of cell membranes
and is synthesized by the body (see Chapter 24). The daily
dietary recommendation for cholesterol is less than 300 mg.
Proteins
Proteins are required for growth and maintenance of body
tissues, enzymes and antibody formation, fluid and electrolyte balance, and nutrient transport. Proteins are com-
Carbohydrates
Dietary carbohydrates are composed of simple sugars,
complex carbohydrates, and undigested carbohydrates
40*
50*
15
25
45
75
90
90
90
90
45
65
75
75
75
75
80
85
85
115
120
120
300
400
600
900
900
900
900
900
600
700
700
700
700
700
750
770
770
1,200
1,300
1,300
Vitamin C
(mg/d)
400*
500*
Vitamin A
(µg/d)a
5*
5*
5*
5*
5*
5*
5*
5*
5*
5*
10*
15*
5*
5*
5*
5*
10*
15*
5*
5*
5*
5*
Vitamin D
(µg/d)b,c
19
19
19
15
15
15
11
15
15
15
15
15
11
15
15
15
15
15
6
7
4*
5*
Vitamin E
(mg/d)d
75*
90*
90*
75*
90*
90*
60*
75*
90*
90*
90*
90*
60*
75*
120*
120*
120*
120*
30*
55*
2.0*
2.5*
Vitamin K
(µg/d)
1.4
1.4
1.4
1.4
1.4
1.4
0.9
1.0
1.1
1.1
1.1
1.1
0.9
1.2
1.2
1.2
1.2
1.2
0.5
0.6
0.2*
0.3*
Thiamin
(mg/d)
1.6
1.6
1.6
1.4
1.4
1.4
0.9
1.0
1.1
1.1
1.1
1.1
0.9
1.3
1.3
1.3
1.3
1.3
0.5
0.6
0.3*
0.4*
Riboflavin
(mg/d)
17
17
17
18
18
18
12
14
14
14
14
14
12
16
16
16
16
16
6
8
2*
4*
Niacin
(mg/d)e
2.0
2.0
2.0
1.9
1.9
1.9
1.0
1.2
1.3
1.3
1.5
1.5
1.0
1.3
1.3
1.3
1.7
1.7
0.5
0.6
0.1*
0.3*
Vitamin B6
(mg/d)
2.8
2.8
2.8
2.6
2.6
2.6
600 j
600 j
600 j
500
500
500
1.8
2.4
2.4
2.4
2.4h
2.4h
1.8
2.4
2.4
2.4
2.4h
2.4h
0.9
1.2
0.4*
0.5*
Vitamin B12
(µg/d)
300
400 i
400 i
400 i
400
400
300
400
400
400
400
400
150
200
65*
80*
Folate
(µg/d)f
7*
7*
7*
6*
6*
6*
4*
5*
5*
5*
5*
5*
4*
5*
5*
5*
5*
5*
2*
3*
1.7*
1.8*
Pantothenic Acid
(mg/d)
35*
35*
35*
30*
30*
30*
20*
25*
30*
30*
30*
30*
20*
25*
30*
30*
30*
30*
8*
12*
5*
6*
Biotin
(µg/d)
550*
550*
550*
450*
450*
450*
375*
400*
425*
425*
425*
425*
375*
550*
550*
550*
550*
550*
200*
250*
125*
150*
Choline g
(mg/d)
Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Vitamins Food and Nutrition Board, Institute of Medicine, National Academies
NOTE: This table (taken from the DRI reports, see www.nap.edu) presents Recommended Dietary Allowances (RDAs) in bold type and Adequate Intakes (AIs) in ordinary type followed by an
asterisk (*) RDAs and AIs may both be used as goals for individual intake. RDAs are set to meet the needs of almost all (97 to 98 percent) individuals in a group. For healthy breastfed infants, the AI
is the mean intake. The AI for other life stage and gender groups is believed to cover needs of all individuals in the group, but lack of data or uncertainty in the data prevent being able to specify
with confidence the percentage of individuals covered by this intake.
a
As retinol activity equivalents (RAEs). 1 RAE = 1 µg retinol, 12 µg β-carotene, 24 µg α-carotene, or 24 µg β-cryptoxanthin. The RAE for dietary provitamin A carotenoids is two-fold greater than
retinol equivalents (RE), whereas the RAE for preformed vitamin A is the same as RE.
b
Cholecalciferol. 1 µg cholecalciferol = 40 IU vitamin D.
c In the absence of adequate exposure to sunlight.
d As α-tocopherol. α-Tocopherol includes RRR-α-tocopherol, the only form of α-tocopherol that occurs naturally in foods, and the 2R-stereoisomeric forms of α-tocopherol (RRR-, RSR-, RRS-, and
RSS-α-tocopherol) that occur in fortified foods and supplements. It does not include the 2S-stereoisomeric forms of α-tocopherol (SRR-, SSR-, SRS-, and SSS-α-tocopherol), also found in fortified
foods and supplements.
e As niacin equivalents (NE). 1 mg of niacin = 60 mg of tryptophan, 0–6 months = preformed niacin (not NE).
f
As dietary folate equivalents (DFE). 1 DFE = 1 µg food folate = 0.6 µg of folic acid from fortified food or as a supplement consumed with food = 0.5 µg of a supplement taken on an empty stomach.
g Although AIs have been set for choline, there are few data to assess whether a dietary supply of choline is needed at all stages of the life cycle, and it may be that the choline requirement can be
met by endogenous synthesis at some of these stages.
h
Because 10 to 30 percent of older people may malabsorb food-bound B12, it is advisable for those older than 50 years to meet their RDA mainly by consuming foods fortified with B12 or a
supplement containing B12.
iIn view of evidence linking folate intake with neural tube defects in the fetus, it is recommended that all women capable of becoming pregnant consume 400 µg from supplements or fortified foods
in addition to intake of food folate from a varied diet.
j It is assumed that women will continue consuming 400 µg from supplements or fortified food until their pregnancy is confirmed and they enter prenatal care, which ordinarily occurs after the end
of the periconceptional period—the critical time for formation of the neural tube.
Copyright 2001 by the National Academy of Sciences. All rights reserved.
Infants
0–6 mo
7–12 mo
Children
1–3 y
4–8 y
Males
9–13 y
14–18 y
19–30 y
31–50 y
51–70 y
>70 y
Females
9–13 y
14–18 y
19–30 y
31–50 y
51–70 y
>70 y
Pregnancy
≤18 y
19–30 y
31–50 y
Lactation
≤18 y
19–30 y
31–50 y
Life Stage
Group
TABLE 11-2
CHAPTER 11 Alterations in Nutritional Status
223
11*
15*
25*
35*
35*
35*
30*
30*
21*
24*
25*
25*
20*
20*
29*
30*
30*
44*
45*
45*
1,300*
1,300*
1,000*
1,000*
1,200*
1,200*
1,300*
1,300*
1,000*
1,000*
1,200*
1,200*
1,300*
1,000*
1,000*
1,300*
1,000*
1,000*
0.2*
5.5*
Chromium
(µg/d)
500*
800*
210*
270*
Calcium
(mg/d)
1,300
1,300
1,300
1,000
1,000
1,000
700
890
900
900
900
900
700
890
900
900
900
900
340
440
200*
220*
Copper
(µg/d)
3*
3*
3*
3*
3*
3*
2*
3*
3*
3*
3*
3*
2*
3*
4*
4*
4*
4*
0.7*
1*
0.01*
0.5*
Fluoride
(mg/d)
290
290
290
220
220
220
120
150
150
150
150
150
120
150
150
150
150
150
90
90
110*
130*
Iodine
(µg/d)
10
9
9
27
27
27
8
15
18
18
8
8
8
11
8
8
8
8
7
10
0.27*
11
Iron
(mg/d)
360
310
320
400
350
360
240
360
310
320
320
320
240
410
400
420
420
420
80
130
30*
75*
Magnesium
(mg/d)
2.6*
2.6*
2.6*
2.0*
2.0*
2.0*
1.6*
1.6*
1.8*
1.8*
1.8*
1.8*
1.9*
2.2*
2.3*
2.3*
2.3*
2.3*
1.2*
1.5*
0.003*
0.6*
Manganese
(mg/d)
50
50
50
50
50
50
34
43
45
45
45
45
34
43
45
45
45
45
17
22
2*
3*
Molybdenum
(µg/d)
1,250
700
700
1,250
700
700
1,250
1,250
700
700
700
700
1,250
1,250
700
700
700
700
460
500
100*
275*
Phosphorus
(mg/d)
70
70
70
60
60
60
40
55
55
55
55
55
40
55
55
55
55
55
20
30
15*
20*
Selenium
(µg/d)
13
12
12
12
11
11
8
9
8
8
8
8
8
11
11
11
11
11
3
5
2*
3
Zinc
(mg/d)
Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Elements Food and Nutrition Board, Institute of Medicine, National Academies
UNIT III
NOTE: This table presents Recommended Dietary Allowances (RDAs) in bold type and Adequate Intakes (AIs) in ordinary type followed by an asterisk (*). RDAs and AIs may both be used as goals
for individual intake. RDAs are set to meet the needs of almost all (97 to 98 percent) individuals in a group. For healthy breastfed infants, the AI is the mean intake. The AI for other life stage and
gender groups is believed to cover needs of all individuals in the group, but lack of data or uncertainty in the data prevent being able to specify with confidence the percentage of individuals
covered by this intake.
SOURCES: Dietary Reference intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997); Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin
B12, Pantothenic Acid, Biotin, and Choline (1998); Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000); and Dietary Reference Intakes for Vitamin A, Vitamin K,
Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). These reports may be accessed via www.nap.edu.
Copyright 2001 by The National Academies of Sciences. All rights reserved.
Infants
0–6 mo
7–12 mo
Children
1–3 y
4–8 y
Males
9–13 y
14–18 y
19–30 y
31–50 y
51–70 y
>70 y
Females
9–13 y
14–18 y
19–30 y
31–50 y
51–70 y
>70 y
Pregnancy
≤18 y
19–30 y
31–50 y
Lactation
≤18 y
19–30 y
31–50 y
Life Stage
Group
TABLE 11-3
224
Integrative Body Functions
CHAPTER 11
TABLE 11-4
Life Stage
Group
Infants
0–6 mo
7–12 mo
Children
1–3 y
4–8 y
Males
9–13 y
14–18 y
19–30 y
31–50 y
51–70 y
>70 y
Females
9–13 y
14–18 y
19–30 y
31–50 y
51–70 y
>70 y
Pregnancy
14–18 y
19–30 y
31–50 y
Lactation
14–18
19–30 y
31–50 y
225
Alterations in Nutritional Status
Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Macronutrients Food
and Nutrition Board, Institute of Medicine, National Academies
α-Linolenic Acid
(g/d)
Proteina
(g/d)
0.5*
0.5*
9.1*
13.5
7*
10*
0.7*
0.9*
13
19
ND
ND
ND
ND
ND
ND
12*
16*
17*
17*
14*
14*
1.2*
1.6*
1.6*
1.6*
1.6*
1.6*
34
52
56
56
56
56
26*
26*
25*
25*
21*
21*
ND
ND
ND
ND
ND
ND
10*
11*
12*
12*
11*
11*
1.0*
1.1*
1.1*
1.1*
1.1*
1.1*
34
46
46
46
46
46
175
175
175
28*
28*
28*
ND
ND
ND
13*
13*
13*
1.4*
1.4*
1.4*
71
71
71
210
210
210
29*
29*
29*
ND
ND
ND
13*
13*
13*
1.3*
1.3*
1.3*
71
71
71
Carbohydrate
(g/d)
Total Fiber
(g/d)
Fat
(g/d)
60*
95*
ND
ND
31*
30*
130
130
19*
25*
ND
ND
130
130
130
130
130
130
31*
38*
38*
38*
30*
30*
130
130
130
130
130
130
Linoleic Acid
(g/d)
4.4*
4.6*
NOTE: This table presents Recommended Dietary Allowances (RDAs) in bold type and Adequate Intakes (AIs) in
ordinary type followed by an asterisk (*). RDAs and AIs may both be used as goals for individual intake. RDAs are set
to meet the needs of almost all (97 to 98 percent) individuals in a group. For healthy breastfed infants, the AI is the
mean intake. The AI for other life stage and gender groups is believed to cover needs of all individuals in the group
but lack of data or uncertainty in the data prevent being able to specify with confidence the percentage of individuals
covered by this intake.
aBased on 0.8g protein/kg body weight for reference body weight.
SOURCE: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino
Acids (2002). This report may be accessed via www.nap.edu.
Copyright 2002 by the National Academy of Sciences. All rights reserved.
(i.e., fiber). Because of their vitamin, mineral, and fiber content, it is recommended that the bulk of the carbohydrate
content in the diet be in the complex form rather than as
simple sugars that contain few nutrients. Sucrose (i.e., table
sugar) is implicated in the development of dental caries.
TABLE 11-5
Overweight
Normal
Underweight
Caloric Requirements Based
on Body Weight and Activity Level
Sedentary
Moderate
Active
20–25 kcal/kg
30 kcal/kg
30 kcal/kg
30 kcal/kg
35 kcal/kg
40 kcal/kg
35 kcal/kg
40 kcal/kg
45–50 kcal/kg
(Adapted from Goodhart R.S., Shils M.E. [1980]. Modern nutrition in health
and disease [6th ed.]. Philadelphia: Lea and Febiger)
There is no specific dietary requirement for carbohydrates. All of the energy requirements of the body can be
met by dietary fats and proteins. Although some tissues,
such as the nervous system, require glucose as an energy
source, this need can be met through the conversion of
amino acids and the glycerol part of the triglyceride molecule to glucose. The fatty acids from triglycerides are converted to ketones and used for energy by other body tissues.
A carbohydrate-deficient diet usually results in the loss of
tissue proteins and the development of ketosis. Because
protein and fat metabolism increases the production of osmotically active metabolic wastes that must be eliminated
through the kidneys, there is danger of dehydration and
electrolyte imbalances. The amount of carbohydrate needed
to prevent tissue wasting and ketosis is 50 to 100 g/day. In
practice, most of the daily energy requirement should be
from carbohydrate. This is because protein is an expensive
226
UNIT III
Integrative Body Functions
source of calories and because it is recommended that no
more than 30% of the calories in the diet be derived from
fat. The AMDR indicates that carbohydrate intake should
be limited to no less than 45% of the calories in the diet to
prevent high intakes of fat.5
Vitamins
Vitamins are a group of organic compounds that act as
catalysts in various chemical reactions. A compound cannot be classified as a vitamin unless it is shown that a deficiency of it causes disease. Contrary to popular belief,
vitamins do not provide energy directly. As catalysts, they
are part of the enzyme systems required for the release of
energy from protein, fat, and carbohydrates. Vitamins also
are necessary for the formation of red blood cells, hormones,
genetic materials, and the nervous system. They are essential for normal growth and development.
There are two types of vitamins: fat soluble and
water soluble. The four fat-soluble vitamins are vitamins
A, D, E, and K. The nine required water-soluble vitamins
are thiamine, riboflavin, niacin, pyridoxine (vitamin B6),
pantothenic acid, vitamin B12, folic acid, biotin, and vitamin C. Because the water-soluble vitamins are excreted
in the urine, they are less likely to become toxic to the
body, as compared with the fat-soluble vitamins that are
stored in the body. Table 11-6 lists sources and functions
of vitamins.
Minerals
Minerals serve many functions. They are involved in acidbase balance and in the maintenance of osmotic pressure in
body compartments. Minerals are components of vitamins,
hormones, and enzymes. They maintain normal hemoglobin levels, play a role in nervous system function, and are
involved in muscle contraction and skeletal development
and maintenance. Minerals that are present in relatively
large amounts in the body are called macrominerals. These
include calcium, phosphorus, sodium, chloride, potassium,
magnesium, and sulfur. The remainder are classified as trace
minerals; they include iron, manganese, copper, iodine,
zinc, cobalt, fluorine, and selenium. Table 11-7 lists mineral
sources and functions.
Fiber
Fiber, the portion of food that cannot be digested by the
human intestinal tract, increases stool bulk and facilitates
bowel movements. Soluble fiber, the type that produces a
gel in the intestinal tract, binds with cholesterol and prevents it from being absorbed by the body. Soluble fiber also
lowers blood glucose. More studies are needed to establish
whether fiber prevents colon cancer and promotes weight
loss. In 2002, the Food and Nutrition Board gave its first
recommended intake for fiber. Men and women who are
50 years and younger should have 38 and 25 grams, respectively, of fiber daily, whereas those older than 50 years
should have 30 and 21 grams, respectively, each day. The
recommendation for children ranges from 19 to 31 grams,
and for teenagers, it is similar to adults.5
NUTRITIONAL ASSESSMENT
The nutritional status can be assessed using the subjective
global assessment (SGA). It includes weight status for the
previous 6 months, dietary intake, gastrointestinal symptoms that impact food intake, and functional capacity and
physical signs of fat loss and muscle wasting. Combined
with objective measures such as albumin levels and body
mass index, SGA will accurately identify malnourished individuals 90% of the time.7
Diet Assessment
A nutritional assessment includes an evaluation of the person’s diet. This can be accomplished by recording the food
consumed or by 24-hour recall and through the administration of a questionnaire or diet history. Each technique
has its own shortcomings, such as the tendency to alter
behavior when it is known that the behavior is being observed or reported.
Health Assessment
Health assessment, including a health history and physical
examination, reveals weight changes, muscle wasting, fat
stores, functional status, and nutritional status. Comparison of the person’s current weight with previous weights
identifies whether the person’s weight is stable, changed
drastically, or tends to fluctuate. For example, recent rapid
weight loss can be a sign of cancer, a malfunctioning thyroid gland, or self-imposed starvation. A history of fluctuating weight could be associated with bulimia. Degradation
of muscle, or muscle wasting, is a serious sign of malnutrition. Decreased ability to initiate or complete activities of
daily living could result from a decrease in energy caused
by a poor diet, a neurologic malfunction such as multiple
sclerosis, or symptoms related to chronic obstructive pulmonary disease. Quality of the hair, absence of body hair,
condition of gums, and skin lesions could signal poor nutritional status.
Anthropometric Measurements
Anthropometric measurements provide a means for assessing body composition, particularly fat stores and skeletal muscle mass. This is done by measuring height, weight,
body circumferences, and thickness of various skinfolds.
These measurements commonly are used to determine
growth patterns in children and appropriateness of current weight in adults.
Body weight is the most frequently used method of
assessing nutritional status; it should be used in combination with measurements of body height to establish
whether a person is underweight or overweight.
An unintentional loss of 10% of body weight or more
within the past 6 months usually is considered predictive of
a poor clinical outcome, especially if weight loss is continuing.8 The body mass index (BMI) uses height and weight
to determine healthy weight (Table 11-8). It is calculated by
dividing the weight in kilograms by the height in meters
squared (BMI = weight [kg]/height [m2]). A BMI between
18.5 and 25 has the lowest statistical health risk.9 A BMI of
CHAPTER 11
TABLE 11-6
Alterations in Nutritional Status
227
Sources and Functions of Vitamins
Vitamin
Major Food Sources
Functions
Fat-Soluble Vitamins
Vitamin A (retinol, provitamin,
carotenoids)
Retinol: liver, butter, whole milk, cheese,
egg yolks; provitamin A: carrots, green
leafy vegetables, sweet potatoes,
pumpkin, winter squash, apricots,
cantaloupe, fortified margarine
Fortified dairy products, fortified
margarine, fish oils, egg yolk
Essential for normal retinal function; plays
an essential role in cell growth and
differentiation, particularly epithelial
cells. Epidemiologic evidence suggests a
role in preventing certain cancers
Increases intestinal absorption of calcium
and promotes ossification of bones and
teeth
Functions as an antioxidant protecting
vitamins A and C and fatty acids;
prevents cell membrane injury
Vitamin D (calciferol)
Vitamin E (tocopherol)
Water-Soluble Vitamins
Vitamin C (ascorbic acid)
Vegetable oil, margarine, shortening, green
and leafy vegetables, wheat germ, wholegrain products, egg yolk, butter, liver
Broccoli, sweet and hot peppers, collards,
brussel sprouts, kale, potatoes, spinach,
tomatoes, citrus fruits, strawberries
Thiamin (vitamin B1)
Pork, liver, meat, whole grains, fortified
grain products, legumes, nuts
Riboflavin (vitamin B2)
Liver, milk, yogurt, cottage cheese, meat,
fortified grain products
Niacin (nicotinamide,
nicotinic acid)
Liver, meat, poultry, fish, peanuts,
fortified grain products
Folacin (folic acid)
Liver, legumes, green leafy vegetables
Vitamin B6 (pyridoxine)
Meat, poultry, fish, shellfish, green and
leafy vegetables, whole-grain products,
legumes
Meat, poultry, fish, shellfish, eggs, dairy
products
Vitamin B12
Biotin
Pantothenic acid
Kidney, liver, milk, egg yolks, most fresh
vegetables
Liver, kidney, meats, milk, egg yolk,
whole-grain products, legumes
Potent antioxidant involved in many
oxidation–reduction reactions; required
for synthesis of collagen; increases absorption of nonheme iron; is involved
in wound healing and drug metabolism
Coenzyme required for several important
biochemical reactions in carbohydrate
metabolism; thought to have an independent role in nerve conduction
Coenzyme that participates in a variety of
important oxidation–reduction reactions
and an important component of a
number of enzymes
Essential component of the coenzymes
nicotinamide adenine dinucleotide
(NAD) and nicotinamide dinucleotide
diphosphate (NADP), which are involved
in many oxidative reduction reactions
Coenzyme in amino acid and nucleoprotein metabolism; promotes red
cell formation
A major coenzyme involved in the metabolism of amino acids; required for
synthesis of heme
Coenzyme involved in nucleic acid synthesis; assists in development of red cells
and maintenance of nerve function
Coenzyme in fat synthesis, amino acid
metabolism, and glycogen formation
Coenzyme involved in energy metabolism
(Data from Vitamin facts, National Dairy Council, and other sources)
less than 18.5 is classified as being underweight, and a BMI
of 25 to 29.9 is considered overweight.10 A BMI greater than
29.9 is diagnosed as obesity and is furthered classified into
class I (BMI, 30.0–34.9), class II (BMI, 35.0–39.9), and class
III or extreme obesity (BMI >40). Body weight reflects both
lean body mass and adipose tissue and cannot be used as a
method for describing body composition or the percentage
of fat tissue present. Statistically, the best percentage of
body fat for men is between 12% and 20%, and for women,
it is between 20% and 30%.10 During physical training,
body fat usually decreases, and lean body mass increases.
Among the methods used to estimate body fat are skinfold thickness, body circumferences, hydrodensitometry,
bioelectrical impedance, dual photon absorptiometry, computed tomography (CT), and magnetic resonance imaging
(MRI). Measurements of skinfold thickness can provide a
reasonable assessment of body fat, particularly if taken at
multiple sites. They can provide information about the location of the fat and can be used, together with equations
and tables, to estimate the percentage of lean body mass
and fat tissue.11,12 However, these measurements often are
difficult to perform and subject to considerable variation
228
UNIT III
TABLE 11-7
Integrative Body Functions
Sources and Functions of Minerals
Mineral
Major Sources
Functions
Calcium
Milk and milk products, fish with bones,
greens
Table salt, meats, milk, eggs
Bone formation and maintenance; tooth formation, vitamin B
absorption, blood clotting, nerve and muscle function
Regulates pH of stomach, acid-base balance, osmotic pressure
of extracellular fluids
Aids in maturation of red blood cells (as part of B12 molecule)
Catalyst for hemoglobin formation, formation of elastin and
collagen, energy release (cytochrome oxidase and catalase),
formation of melanin, formation of phospholipids for
myelin sheath of nerves
Strengthens bones and teeth
Thyroid hormone synthesis and its function in maintenance
of metabolic rate
Hemoglobin synthesis, cellular energy release (cytochrome
pathway), killing bacteria (myeloperoxidase)
Chloride
Cobalt
Copper
Organ meats, meats
Cereals, nuts, legumes, liver, shellfish,
grapes, meats
Fluoride
Iodine
Fluorinated water
Iodized salt, fish (saltwater and
anadromous)
Meats, heart, liver, clams, oysters, lima
beans, spinach, dates, dried nuts,
enriched and whole-grain cereals
Milk, green vegetables, nuts, bread, cereals
Iron
Magnesium
Phosphorus
Meats, poultry, fish, milk and cheese,
cereals, legumes, nuts
Potassium
Oranges, dried fruits, bananas, meats,
potatoes, peanut butter, coffee
Sodium
Table salt, cured meats, meats, milk,
olives
Zinc
Whole-wheat cereals, eggs, legumes
TABLE 11-8
Catalyst of many intracellular nerve impulses, retention of
reactions, particularly those related to intracellular enzyme
reactions; low magnesium levels produce an increase in
irritability of the nervous system, vasodilatation, and
cardiac dysrhythmias
Bone formation and maintenance; essential component of
nucleic acids and energy exchange forms such as adenosine
triphosphate (ATP)
Maintenance of intracellular osmolality, acid-base balance,
transmission of nerve impulses, catalyst in energy
metabolism, formation of proteins, formation of glycogen
Maintenance of osmotic pressure of extracellular fluids, acidbase balance, neuromuscular function; absorption of
glucose
Integral part of many enzymes, including carbonic anhydrase,
which facilitates combination of carbon dioxide with water
in red blood cells; component of lactate dehydrogenase,
which is important in cellular metabolism; component of
many peptidases; important in digestion of proteins in
gastrointestinal tract
Classification of Overweight and Obesity by BMI, Waist Circumference,
and Associated Disease Risk*
Disease Risk* Relative to Normal Weight
and Waist Circumference
BMI
(kg/m2)
Underweight
Normal†
Overweight
Obesity
Extreme obesity
<18.5
18.5–24.9
25.0–29.9
30.0–34.9
35.0–39.9
≥40
Obesity
Class
Men ≤102 cm (≤40 in)
Women ≤88 cm (≤35 in)
Men >102 cm (>40 in)
Women >88 cm (>35 in)
I
II
III
—
—
Increased
High
Very high
Extremely high
—
—
High
Very high
Very high
Extremely high
BMI, body mass index.
*Disease risk for type 2 diabetes, hypertension, and cardiovascular disease.
† Increased waist circumference also can be a marker for increased risk, even in persons of normal weight.
(Expert Panel. [1998]. Clinical guidelines on the identification, evaluation, and treatment of overweight and
obesity in adults. National Institutes of Health. [On-line.] Available:
http://nhlbi.nih.gov/guidelines/ob_gdlns.htm.
CHAPTER 11
between observers, and they do not provide information
about abdominal and intramuscular fat.
The measurement of body circumferences has received
attention because excess visceral or intraabdominal fat is associated with increased risk for diabetes and cardiovascular
disease.13 Studies have also indicated that the subcutaneous
fat at the abdomen is highly correlated with insulin resistance. A waist circumference greater than 40 inches in men
and greater than 35 inches in women is considered high
risk.13 The remaining methods of determining body fat except for bioimpedance are expensive and not portable and
are usually done in research settings. Bioimpedance is performed by attaching electrodes at the wrist and ankle that
send a harmless current through the body. The flow of the
current is affected by the amount of water in the body. Because fat-free tissue contains virtually all the water and
the conducting electrolytes, measurements of the resistance
(i.e., impedance) to current flow can be used to estimate the
percentage of body fat present.
Laboratory Studies
Various laboratory tests can aid in evaluating nutritional
status. Some of the most commonly performed tests are
serum albumin and prealbumin to assess the protein status, total lymphocyte count and delayed hypersensitivity
reaction to assess cellular immunity, and creatinine–height
index to assess skeletal muscle protein. Vitamin and mineral deficiencies can be determined by measurements of
their levels in blood, saliva, and other body tissues or by
measuring nutrient-specific chemical reactions. All of these
tests are limited by confounding factors and therefore need
to be evaluated along with other clinical data.
In summary, nutritional status describes the condition of the
body related to the availability and use of nutrients. Nutrients
provide the energy and materials necessary for performing the
activities of daily living and for the growth and repair of body
tissues. Metabolism is the organized process whereby nutrients such as carbohydrates, fats, and proteins are broken
down, transformed, or otherwise converted to cellular energy.
Glucose, fats, and amino acids from proteins serve as fuel
sources for cellular metabolism. These fuel sources are ingested during meals and stored for future use. Glucose is
stored as glycogen or converted to triglycerides in fat cells for
storage. Fats are stored in adipose tissue as triglycerides.
Amino acids are the building blocks of proteins, and most of
the stored amino acids are contained in body proteins and as
fuel sources for cellular metabolism. Energy is measured in
heat units called kilocalories.
The expenditure of body energy results from heat production (i.e., thermogenesis) associated with the BMR or basal energy equivalent, diet-induced thermogenesis, exercise-induced
thermogenesis, and thermogenesis in response to changes in
environmental conditions.
The body requires more than 40 nutrients on a daily basis.
Nutritional status reflects the continued daily intake of nutrients over time and the deposition and use of these nutrients
in the body. The DRI is the Daily Recommended Intake of essential nutrients considered to be adequate to meet the known
Alterations in Nutritional Status
229
nutritional needs of healthy persons. The DRI has 22 age and
sex classifications and includes recommendations for calories,
protein, fat, carbohydrates, vitamins, and minerals. The nutritional status of a person can be assessed by evaluation of
dietary intake, anthropometric measurements, health assessment, and laboratory tests. Health assessment includes a
health history and physical examination to determine weight
changes, muscle wasting, fat stores, functional status, and nutritional status. Anthropometric measurements are used for assessing body composition; they include height and weight
measurements and measurements to determine the composition of the body in relation to lean body mass and fat tissue
(e.g., skinfold thickness, body circumferences, hydrodensitometry, bioelectrical impedance, and CT scans).
Overnutrition and Obesity
After completing this section of the chapter, you should be able to
meet the following objectives:
✦ Define and discuss the causes of obesity and health risks
associated with obesity
✦ Differentiate upper and lower body obesity and their
implications in terms of health risk
✦ Discuss the treatment of obesity in terms of diet,
behavior modification, exercise, social support, and
surgical methods
Obesity is defined as a condition characterized by excess body fat. Clinically, obesity and overweight have been
defined in terms of the BMI. Historically, various world
bodies have used different BMI cutoff points to define obesity. In 1997, the World Health Organization defined the
various classifications of overweight (BMI ≥25) and obesity
(BMI ≥30). This classification was subsequently adopted by
the National Institutes of Health (NIH).13 The use of a BMI
cutoff of 25 as a measure of overweight raised some concern that the BMI in some men might be due to muscle
rather than fat weight. However, it has been shown that a
BMI cutoff of 25 can sensitively detect most overweight
people and does not erroneously detect overlean people.14
Overweight and obesity have become national health
problems, increasing the risk for hypertension, hyperlipidemia, type 2 diabetes, coronary heart disease, and other
health problems. Sixty-four and one-half percent of the U.S.
population is estimated to be overweight (BMI ≥25), and
30.5% of the population is obese (BMI ≥30).15 There was no
difference in prevalence among men of different racial and
ethnic groups. However, black women had a significantly
higher rate of overweight and obesity than did white
women. Hispanic women fell between the two groups. The
prevalence in overweight and obesity is alarming not only
because of the number of people affected but also because
the prevalence continues to increase from previous surveys.
The prevalence of severe obesity is increasing at an even
faster rate, with persons who self-reported a BMI of at least
40 having increased from 1 in 200 to 1 in 50; those with a
230
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Integrative Body Functions
BMI of at least 50 from 1 in 2000 to 1 in 400; and those with
a BMI of at least 30 from 1 in 10 to 1 in 5.16
CAUSES OF OBESITY
The excess body fat of obesity often significantly impairs
health, and as a result, obesity is the second leading cause
of preventable death in the United States.17 This excess
body fat is generated when the calories consumed exceed
those expended through exercise and activity.18 Although
factors that lead to the development of obesity are not well
understood, they are thought to involve the interaction of
genotype and environmental factors, which include social,
behavioral, and cultural, with the physiology, metabolism,
and genetics of the individual.19
In studies of persons who were overweight, the metabolic factors contributing to overweight were a low energy
expenditure rate; a high respiratory quotient (RQ), which
indicates the carbohydrate-to-fat oxidation ratio; and a
low level of spontaneous physical activity.20 The average
adjusted energy expenditure of overweight persons was
36.3 kcal/kg fat-free mass (FFM) but could range from 28
to 42 kcal/kg FFM. The RQ was likely to be high in those
who gained weight, suggesting that the person was oxidizing more carbohydrate than fat.
Epidemiologic surveys indicate that the prevalence of
overweight may also be related to social and economic conditions. The second (1976 through 1980) National Health
and Nutrition Examination Survey (NHANES II) has shown
that if American women are divided into two groups according to economic status, the prevalence of obesity is
much higher among those in the poverty group.21 In contrast, men above the poverty level had a higher prevalence
of overweight than men below the poverty level.
Obesity is known to run in families, suggesting a hereditary component. The question that surrounds this observation is whether the disorder arises because of genetic
endowment or environmental influences. Studies of twins
and adopted children have provided evidence that heredity contributes to the disorder.22 It is now believed that the
heritability of the BMI is between 30% and 40%.20
Although genetic factors may explain some of the individual variations in terms of excess weight, environmental influences also must be taken into account. These
influences include family dietary patterns, decreased level
of activity because of labor-saving devices and time spent
on the computer, reliance on the automobile for transportation, easy access to food, energy density of food, and
super sizing of portions. The obese may be greatly influenced by the availability of food, the flavor of food, time
of day, and other cues. The composition of the diet also
may be a causal factor, and the percentage of dietary fat independent of total calorie intake may play a part in the development of obesity. Psychological factors include using
food as a reward, comfort, or means of getting attention.
Eating may be a way to cope with tension, anxiety, and
mental fatigue. Some persons may overeat and use obesity
as a means of avoiding emotionally threatening situations.
It has been suggested that the increased prevalence of
obesity in the United States has resulted from increased
caloric intake together with a sedentary lifestyle and
energy-saving conveniences.23 Even when a reasonable
number of calories are consumed, fewer are expended because of inactivity. A low rate of energy expenditure may
contribute to the prevalence of obesity in some families.
UPPER AND LOWER BODY OBESITY
Two types of obesity based on distribution of fat have been
described: upper body and lower body obesity. Upper body
obesity is also referred to as central, abdominal, or male obesity. Lower body obesity is known as peripheral, glutealfemoral, or female obesity. The obesity type is determined
by dividing the waist by the hip circumference. A waist-tohip ratio greater than 1.0 in men and 0.8 in women indicates upper body obesity (Fig. 11-4). Research suggests that
fat distribution may be a more important factor for morbidity and mortality than overweight or obesity.
The presence of excess fat in the abdomen out of proportion to total body fat is an independent predictor of risk
factors and mortality. Waist circumference is positively correlated with abdominal fat content. Waist circumference of
OBESITY
➤ Obesity results from an imbalance between energy intake
and energy consumption. Because fat is the main storage
form of energy, obesity represents an excess of body fat.
➤ Overweight and obesity are determined by measurements
of body mass index (BMI; weight [kg]/height [m2]) and
waist circumference. A BMI of 25 to 29.9 is considered
overweight; a BMI of 30 or greater as obese; and a BMI
greater than 40 as very or morbidly obese.
➤ Waist circumference is used to determine the distribution
of body fat. Central, or abdominal, obesity is an independent predictor of morbidity and mortality associated with
obesity.
Fat
biopsy
FIGURE 11-4 Distribution of body fat and size of fat cells in persons
with upper and lower body obesity. (Courtesy of Ahmed Kissebah,
M.D., Ph.D., Medical College of Wisconsin, Milwaukee)
CHAPTER 11
35 inches or greater in women and 40 inches or greater in
men has been associated with increased health risk13 (see
Table 11-8). Central obesity can be further differentiated
into intraabdominal (viscera) fat and subcutaneous fat by
the use of CT or MRI scans. However, intraabdominal fat
usually is synonymous with central fat distribution. One of
the characteristics of abdominal fat is that fatty acids released from the viscera go directly to the liver before entering the systemic circulation, having a potentially greater
impact on hepatic function. Higher levels of circulating
free fatty acids in obese persons, particularly those with
upper body obesity, are thought to be associated with many
of the adverse effects of obesity.18
In general, men have more intraabdominal fat and
women more subcutaneous fat. As men age, the proportion
of intraabdominal fat to subcutaneous fat increases. After
menopause, women tend to acquire more central fat distribution. Increasing weight gain, alcohol, and low levels
of activity are associated with upper body obesity. These
changes place persons with upper body obesity at greater
risk for ischemic heart disease, stroke, and death independent of total body fat. They also tend to exhibit hypertension, elevated levels of triglycerides and decreased levels of
high-density lipoproteins, hyperinsulinemia and diabetes
mellitus, breast and endometrial cancer, gallbladder disease, menstrual irregularities, and infertility. Visceral fat
also is associated with abnormalities of metabolic and sex
hormone levels.24
Weight loss causes a loss of visceral fat and has resulted in improvements in metabolic and hormonal abnormalities.25,26 Although peripheral obesity is associated
with varicose veins in the legs and mechanical problems,
it does not increase the risk for heart disease.27 In terms of
weight reduction, some studies have shown that persons
with upper body obesity are easier to treat than those with
lower body obesity. Other studies have shown no difference in terms of success with weight reduction programs
between the two types of obesity.
Weight cycling (the losing and gaining of weight) has
been found to have little or no effect on metabolic variables, central obesity, or cardiovascular risk factors or future amount of weight loss.28 More research is needed to
determine its effect on dietary preference for fat, psychological adjustment, disordered eating, and mortality.29,30 It
is postulated that perhaps it is the underlying obesity and
not the weight fluctuation that affects life expectancy.31
HEALTH RISKS ASSOCIATED WITH OBESITY
Obesity affects both psychosocial and physical well-being.
In the United States as well as other countries, there are
many negative stereotypes associated with obesity. People,
especially women, are expected to be thin, and obesity may
be seen as a sign of a lack of self-control. Obesity may negatively affect employment and educational opportunities as
well as marital status. Obesity also may play a role in a person’s treatment by health professionals.32 Although nurses,
physicians, and other health professionals are aware of the
low success rate and difficulty in treating weight problems,
they still may place the blame on the obese patient.32
Alterations in Nutritional Status
231
In terms of health problems, obese persons are more
likely to have high blood pressure, hyperlipidemia, cardiovascular disease, stroke, glucose intolerance, insulin resistance, type II diabetes, stroke, gallbladder disease, infertility, and cancer of the endometrium, prostate, colon,
uterine, ovaries, kidney, gallbladder, and in postmenopausal women, breast.20 The increased weight associated
with obesity stresses the bones and joints, increasing the
likelihood of arthritis. Other conditions associated with
obesity include sleep apnea and pulmonary dysfunction,
asthma, complications of pregnancy, menstrual irregularities, hirsutism, psychological distress, nonalcoholic steatohepatitis, carpal tunnel syndrome, venous insufficiency
and deep vein thrombosis, and poor wound healing.20 Because some drugs are lipophilic and exhibit increased distribution in fat tissue, the administration of these drugs, including some anesthetic agents, can be more dangerous in
obese persons. If surgery is required, the obese person heals
slower than a nonobese person of the same age.
Massive obesity, because of its close association with
so many health problems, can be regarded as a disease in
its own right.33 It is the second leading cause of preventable death. In men who have never smoked, the risk for
death increases from 1.06 at a BMI of 24.5 to 1.67 at a BMI
higher than 26.34 The waist-to-hip ratio is a less reliable
predictor of mortality in women than BMI.
PREVENTION OF OBESITY
Emphasis is being placed on the prevention of obesity. It
has been theorized that obesity is largely preventable because hereditary factors exert only a moderate effect.
Some experts indicate that prevention should focus on
young children, adolescents, and young adults,35 while
others would target the high-risk period from 25 to 35 years,
menopause, and the year after successful weight loss.36 A
more active lifestyle together with a low-fat diet (<30% of
calories) is seen as a strategy for prevention. Other strategies include the promotion of regular meals, avoidance of
snacking, substituting water for calorie-containing beverages, decreased television viewing time, and increased
activity.
TREATMENT OF OBESITY
The current recommendation is that treatment is indicated
in all individuals who have a BMI of 30 or higher and those
with a BMI of 25 to 29.9 or a high waist circumference plus
two or more risk factors.37 Treatment should focus on individualized lifestyle modification through a combination of
a reduced-calorie diet, increased physical activity, and behavior therapy. Pharmacotherapy and surgery are available
as an adjunct to lifestyle changes in individuals who meet
specific criteria.
Before treatment begins, an assessment should be made
of the degree of overweight and the overall risk status. The
person should be assessed for the following risk factors:
coronary heart disease and other atherosclerotic diseases,
type 2 diabetes, sleep apnea, gynecologic abnormalities,
osteoarthritis, gallstones, stress incontinence, cigarette
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Integrative Body Functions
smoking, hypertension, low-density lipoprotein cholesterol
greater than 160 mg/dL, high-density lipoprotein cholesterol less than 35 mg/dL, impaired fasting glucose, family
history of premature coronary heart disease, age 45 years
or older in men or 55 years or older in women, physical inactivity, and high triglycerides.38
It also is advisable to determine the person’s motivation to lose weight. Several factors can be evaluated to make
this assessment. These include reasons and motivations for
weight loss, previous history of weight loss attempts, social
support, attitude toward physical activity, ability to participate in physical activity, time available for attempting intervention, understanding the causes of the obesity and its
contribution to disease, and, finally, barriers the patient has
for making changes.
The goals for weight loss are, at a minimum, prevention of further weight gain, but preferably reduction of current weight, and maintenance of a lowered body weight
indefinitely. An algorithm has been designed for use in
treating overweight and obesity. The initial goal in treatment is to lower body weight by 10% from baseline over a
6-month period with a 1- to 2-lb weight loss per week.
Greater rates of weight loss do not achieve better long-term
results.38 This degree of weight loss requires a calorie reduction of 300 to 500 kcal/day in individuals with a BMI
of 27 to 35. For those persons with a BMI greater than 35,
the calorie intake needs to be reduced by 500 to 1000 kcal/
day. After 6 months, the person should be given strategies
for maintaining the new weight. Further weight loss can be
considered after a period of weight maintenance. The person who is unable to achieve significant weight loss should
be enrolled in a weight management program to prevent
further weight gain.
Dietary Therapy
Dietary therapy should be individually prescribed based
on the person’s overweight status and risk profile. The diet
should be a personalized plan that is 500 to 1000 kcal/day
less than the current dietary intake. If the patient’s risk status warrants it, the diet also should be decreased in saturated fat and contain 30% or less of total calories from fat.
Reduction of dietary fat without a calorie deficit will not
result in weight loss. Frequent contacts with a qualified dietetic professional help to achieve weight loss and then to
maintain weight.
Physical Activity
Physical activity is important in the prevention of weight
gain. In addition, it reduces cardiovascular and diabetes
risk beyond that achieved by weight loss alone. Although
physical activity is an important part of weight loss therapy, it does not lead to a significant weight loss. It may,
however, help reduce body fat and prevent the decrease in
muscle mass that often occurs with weight loss. Exercise
should be started slowly with the duration and intensity
increased independent of each other. The goal should be
30 minutes or more of moderate-intensity activity on most
days of the week. The activity can be performed at one
time or intermittently over the day.
Behavior Therapy
Techniques for changing behavior include self-monitoring
of eating habits and physical activity, stress management,
stimulus control, problem solving, contingency management, cognitive restructuring, social support, and relapse
prevention.
Pharmacotherapy
Drugs approved by the FDA can be used as an adjunct to
the aforementioned regimen in some patients with a BMI
of 30 or more with no other risk factors or diseases and for
patients with a BMI of 27 to 29.9 with concomitant risk
factors or disease. The risk factors and diseases defined as
warranting pharmacotherapy are coronary heart disease,
type 2 diabetes, metabolic syndrome, gynecologic abnormalities, osteoarthritis, gallbladder disease, stress incontinence, and sleep apnea.39
Two FDA-approved prescription drugs are available
for long-term weight loss therapy—sibutramine and orlistat. Sibutramine inhibits the reuptake of serotonin, norepinephrine, and dopamine. The drug produces weight
loss by decreasing appetite.40 Orlistat is a lipase inhibitor
that works by decreasing fat absorption in the intestine.
Both sibutramine and orlistat need careful monitoring
for side effects. They also are contraindicated in certain
patients.
Medication produces a 5% to 10% weight loss in clinical trials. This will provide medical benefit. Patients who
do not lose a minimum of 4 pounds in the first 4 to 8 weeks
of drug therapy should be considered nonresponders, and
another antiobesity drug could be tried.39 Even after weight
loss has stopped, the medication can be continued as a part
of a weight-maintenance program.
Over-the-counter (OTC) weight-loss products are not
FDA regulated and should be used with a great deal of
caution.
Weight Loss Surgery
The option of surgery is limited to persons with a BMI
greater than 40; those with a BMI greater than 35 who have
comorbid conditions and in whom efforts at medical therapy have failed; and those who have complications of extreme obesity. Vertical gastric banding and gastric bypass
are two procedures that are used in subjects with acceptable
operative risks. Persons who undergo surgical interventions
also must continue in a program that provides guidance in
nutrition and physical activity and behavioral and social
support. These types of surgery have been shown to result
in a reduction in BMI by 13.3 kg/m2.41
CHILDHOOD OBESITY
Obesity is the most prevalent nutritional disorder affecting
the pediatric population in the United States. The findings
from NHANES III, conducted between 1999 and 2000, indicated that 15% of children from ages 6 to 19 years were
overweight.42 This was a 4% increase from the previous
NHANES study. Ten percent of children 2 to 5 years of age
CHAPTER 11
were overweight. The increase in prevalence was greater for
those of African-American and Hispanic ethnicity. The definition for overweight for the NHANES III study was a BMI
at or above the sex- and age-specific 95th percentile. Those
who were between the 85th and 95th percentile were
defined as at risk for overweight.
The major concern of childhood obesity is that obese
children will grow up to become obese adults. Pediatricians
are now beginning to see hypertension, dyslipidemia, and
type 2 diabetes in obese children and adolescents. In North
America, type 2 diabetes now accounts for half of all new
diagnoses of diabetes (types 1 and 2) in some populations
of adolescents.43 In addition, there is a growing concern
that childhood and adolescent obesity may be associated
with negative psychosocial consequences such as low selfesteem and discrimination by adults and peers.44
Childhood obesity is determined by a combination of
hereditary and environmental factors. It is associated with
obese parents, higher socioeconomic status, increased parental education, small family size, and sedentary lifestyle.45
Children with overweight parents are at highest risk; the
risk in those with two overweight parents is much higher
than that in children of families in which neither parent is
obese. One of the trends leading to childhood obesity is the
increase in inactivity. Increasing perceptions that neighborhoods are unsafe has resulted in less time spent outside
playing and walking and more time spent indoors engaging in sedentary activities such as television viewing and
computer usage. Television viewing is associated with consumption of calorie-dense snacks and decreased indoor activity. Studies have shown a 10% decrease in obesity risk for
each hour per day of moderate-to-vigorous physical activity, whereas the risk increased by 12% for each hour per day
of television viewing.46 Obese children also may have a
deficit in recognizing hunger sensations, stemming perhaps from parents who use food as gratification. The impact of fast food, increased portion size, energy density,
sugar-sweetened soft drinks, and high glycemic index foods
all are likely contributing to the increased weights in children and adolescents.
Because adolescent obesity is predictive of adult obesity, treatment of childhood obesity is desirable.47 The goals
of therapy in uncomplicated obesity are directed toward
healthy eating and activity, not achievement of ideal body
weight.48 Families should be taught awareness of current
eating habits, activity, and parenting behavior and how to
modify them. In children with complications secondary to
the obesity, the medial goal should be to improve that
problem. Maintenance of baseline weight should be the
initial step in weight control for all overweight children
2 years of age and older.48 Children who have secondary
complications of obesity will benefit from changes in eating and activity that will lead to weight loss of approximately 1 pound per month.47 The weight loss interventions
should include all family members and caregivers; begin
early at a point when the family is ready for change; assist
the family in learning to monitor eating and activity patterns and to make small and acceptable changes in these
patterns; and teach the family to encourage and emphasize, not criticize.48 They should include information about
Alterations in Nutritional Status
233
the medical complications of obesity, and they should be
directed at permanent changes, not short-term diets or exercise programs aimed at rapid weight loss. Approaches
can include a reduction of inactivity by limitation of television and computer and video games and by building activity into daily routine and on most days encouraging
30 minutes of unstructured outdoor play. Dietary goals are
well-balanced, healthy meals with a healthy approach to
eating using the Food Guide Pyramid as a model.49 Specific
strategies can include reduction of specific high-calorie
foods or an appropriate balance of foods that are low,
medium, and high calorie. Commercial diets are not recommended. Pharmacologic therapy and bariatric surgery
should be reserved for children with complications and for
severe obesity, respectively.46
In summary, obesity is defined as excess body fat resulting
from consumption of calories in excess of those expended for
exercise and activities. Heredity, socioeconomic, cultural, and
environmental factors, psychological influences, and activity
levels have been implicated as causative factors in the development of obesity. The health risks associated with obesity include hypertension and cardiovascular disease, hyperlipidemia,
insulin resistance and type 2 diabetes mellitus, menstrual irregularities and infertility, cancer of the endometrium, breast,
prostate, and colon, and gallbladder disease. There are two
types of obesity—upper body and lower body obesity. Upper
body obesity is associated with a higher incidence of complications. The treatment of obesity focuses on nutritionally adequate weight-loss diets, behavior modification, exercise, social
support, and, in situations of marked obesity, surgical methods.
Obesity is the most prevalent nutritional disorder affecting the
pediatric population in the United States.
Undernutrition
After completing this section of the chapter, you should be able to
meet the following objectives:
✦ List the major causes of malnutrition and starvation
✦ State the difference between protein-calorie starvation
(i.e., marasmus) and protein malnutrition (i.e., kwashiorkor)
✦ Explain the effect of malnutrition on muscle mass,
respiratory function, acid-base balance, wound healing,
immune function, bone mineralization, the menstrual
cycle, and testicular function
✦ State the causes of malnutrition in the hospitalized patient
✦ Compare the eating disorders and complications associated with anorexia nervosa, bulimia nervosa, and the
binge-purge syndrome
Undernutrition ranges from the selective deficiency of
a single nutrient to starvation in which there is deprivation
of all ingested nutrients. Undernutrition can result from
willful eating behaviors, as in anorexia nervosa and the
binge-purge syndrome; lack of food availability; or health
problems that impair food intake and decrease its absorption
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Integrative Body Functions
and use. Weight loss and malnutrition are common during illness, recovery from trauma, and hospitalization.
The prevalence of malnutrition in children is substantial. Globally, nearly 195 million children younger
than 5 years of age are undernourished.50 Malnutrition is
most obvious in developing countries of the world, where
the condition takes severe forms. Even in developed nations,
malnutrition remains a problem. In 1992, it was estimated
that 12 million American children consumed diets that
were significantly below the recommended allowances of
the National Academy of Sciences.50
MALNUTRITION AND STARVATION
Malnutrition and starvation are conditions in which a person does not receive or is unable to use an adequate amount
of calories and nutrients for body function. Among the
many causes of starvation, some are willful, such as the person with anorexia nervosa who does not consume enough
food to maintain weight and health, and some are medical,
such as persons with Crohn’s disease who are unable to absorb their food. Most cases of food deprivation result in
semistarvation with protein and calorie malnutrition.
In malnutrition and starvation, the amount of food
consumed and absorbed is drastically reduced. It may be
primary, resulting from inadequate food intake, or secondary to disease conditions that produce tissue wasting.
Most of the literature on malnutrition and starvation has
dealt with infants and children in underdeveloped countries. Malnutrition in this population commonly is divided
into two distinct conditions: marasmus and kwashiorkor.
Marasmus represents a progressive loss of muscle mass
and fat stores resulting from inadequate food intake that is
equally deficient in calories and protein. The person appears
emaciated, with sparse, dry, and dull hair and depressed
heart rate, blood pressure, and body temperature. The
child with marasmus has a wasted appearance, with stunted
growth and loss of subcutaneous fat, but with relatively normal skin, hair, and liver function. Kwashiorkor is caused by
protein deficiency. The term kwashiorkor comes from the
African word meaning “the disease suffered by the displaced child” because the condition develops soon after a
child is displaced from the breast after the arrival of a new
infant and placed on a starchy gruel feeding. The child with
kwashiorkor is characterized by edema, desquamating skin,
discolored hair, enlarged abdomen, anorexia, and extreme
apathy. There is less weight loss and wasting of skeletal
muscles than in marasmus. Other manifestations include
skin lesions, easily pluckable hair, enlarged liver and distended abdomen, cold extremities, and decreased cardiac
output and tachycardia. Marasmus-kwashiorkor is an advanced protein-calorie deficit together with increased protein requirement or loss. This results in a rapid decrease in
anthropometric measurements with obvious edema and
wasting and loss of organ mass.
fat-free, metabolically active tissues of the body, namely,
the skeletal muscles, viscera, and cells of the blood and immune system. They account for 35% to 50% of the total
weight in the healthy young adult, with fat (20% to 30%),
extracellular fluid (20%), and skeletal and connective tissues (10% to 15%).51 Because the lean tissues are the largest
body compartment, their rate of loss is the main determinant of total body weight in most cases of protein-calorie
malnutrition.
Protein-calorie malnutrition is common in persons
with trauma, sepsis, and serious illnesses such as cancer and
acquired immunodeficiency syndrome. Approximately half
of all persons with cancer experience tissue wasting in
which the tumor induces metabolic changes leading to a
loss of adipose tissue and muscle mass.52 In healthy adults,
body protein homeostasis is maintained by a cycle in which
the net loss of protein in the postabsorptive state is matched
by a net postprandial gain of protein.53,54 In persons with severe injury or illness, net protein breakdown is accelerated
and protein rebuilding disrupted. Consequently, these persons may lose up to 20% of body protein, much of which
originates in skeletal muscle.49 Protein mass is lost from the
liver, gastrointestinal tract, kidneys, and heart. As protein is
lost from the liver, hepatic synthesis of serum proteins decreases, and decreased levels of serum proteins are observed.
There is a decrease in immune cells. Wound healing is poor,
and the body is unable to fight off infection because of
multiple immunologic malfunctions throughout the body.
The gastrointestinal tract undergoes mucosal atrophy with
loss of villi in the small intestine, resulting in malabsorption. The loss of protein from cardiac muscle leads to a decrease in myocardial contractility and cardiac output. The
muscles used for breathing become weakened, and respiratory function becomes compromised as muscle proteins are
used as a fuel source. A reduction in respiratory function
has many implications, especially for persons with burns,
trauma, infection, or chronic respiratory disease and for
persons who are being mechanically ventilated because of
respiratory failure.
In hospitalized patients, malnutrition increases morbidity and mortality rates, incidence of complications, and
length of stay. Malnutrition may present at the time of admission or develop during hospitalization. The hospitalized patient often finds eating a healthful diet difficult and
commonly has restrictions on food and water intake in
preparation for tests and surgery. Pain, medications, special diets, and stress can decrease appetite. Even when the
patient is well enough to eat, being alone in a room where
unpleasant treatments may be given is not conducive to
eating. Although hospitalized patients may appear to need
fewer calories because they are on bed rest, their actual
need for caloric intake may be higher because of other
energy expenditures. For example, more calories are expended during fever, when the metabolic rate is increased.
There also may be an increased need for protein to support
tissue repair after trauma or surgery.
Protein-Calorie Malnutrition
Protein-calorie malnutrition represents a depletion of the
body’s lean tissues caused by starvation or a combination
of starvation and catabolic stress. The lean tissues are the
Diagnosis
No single diagnostic measure is sufficiently accurate to
serve as a reliable test for malnutrition. Techniques of nu-
CHAPTER 11
tritional assessment include evaluation of dietary intake,
anthropometric measurements, clinical examination, and
laboratory tests. Evaluation of weight is particularly important. Body weight can be assessed in relation to height
using the BMI. Evaluation of body composition can be performed by inspection or using anthropometic measurements such as skin-fold thickness. Serum albumin and
prealbumin are used in the diagnosis of protein-calorie
malnutrition. Albumin, which has historically been used
as a determinant of nutrition status, has a relatively large
body pool and a half-life of 20 days and is less sensitive to
changes in nutrition than prealbumin, which has a shorter
half-life and a relatively small body pool.55
Treatment
The treatment of severe protein-calorie malnutrition involves the use of measures to correct fluid and electrolyte
abnormalities and replenish proteins, calories, and micronutrients.56 Treatment is started with modest quantities
of proteins and calories based on the person’s actual weight.
Concurrent administration of vitamins and minerals is
needed. Either the enteral or parenteral route can be used.
The treatment should be undertaken slowly to avoid complications. The administration of water and sodium with
carbohydrates can overload a heart that has been weakened by malnutrition and result in congestive failure. Enteral feedings can result in malabsorptive symptoms due
to abnormalities in the gastrointestinal tract. Refeeding
edema is a benign dependent edema that results from
renal retention of sodium and poor skin and blood vessel
integrity. It is treated by elevation of the dependent area
and modest sodium restrictions. Diuretics are ineffective
and may aggravate electrolyte deficiencies.
EATING DISORDERS
Eating disorders affect an estimated 5 million Americans
each year.57 These illnesses, which include anorexia nervosa, bulimia nervosa, and binge-eating disorder and their
variants, incorporate serious disturbances in eating, such as
restriction of intake and binging, with an excessive concern
over body shape or body weight. Eating disorders typically
occur in adolescent girls and young women, although 5%
to 15% of cases of anorexia nervosa and 40% of cases of
binge-eating disorder occur in boys and men.57 The mortality rate from anorexia nervosa, 0.56% per year, is more
than 12 times the mortality rate among young women in
the general population.57
Eating disorders are more prevalent in industrialized
societies and occur in all socioeconomic and major ethnic
groups. A combination of genetic, neurochemical, developmental, and sociocultural factors is thought to contribute
to the development of the disorders.58,59 The American Psychiatric Society’s Diagnostic and Statistical Manual of Mental
Disorders, Text Revision (DSM-IV-TR) has established criteria
for the diagnosis of anorexia nervosa and bulimia nervosa.60
Although these criteria allow clinicians to make a diagnosis
in persons with a specific eating disorder, the symptoms
often occur along a continuum between those of anorexia
nervosa and bulimia nervosa. Preoccupation with weight
Alterations in Nutritional Status
235
EATING DISORDERS
➤ Eating disorders are serious disturbances in eating, such as
willful restriction of intake and binge eating, as well as
excessive concern over body weight and shape.
➤ Anorexia nervosa is characterized by a refusal to maintain
a minimally normal body weight (e.g., at least 85% of minimal expected weight); an excessive concern over gaining
weight and how the body is perceived in terms of size and
shape; and amenorrhea (in girls and women after
menarche).
➤ Bulimia nervosa is characterized by recurrent binge eating;
inappropriate compensatory behaviors such as self-induced
vomiting, fasting, or excessive exercise that follow the
binge-eating episode; and extreme concern over body
shape and weight.
➤ Binge eating consists of consuming unusually large quantities of food during a discrete period (e.g., within any 2-hour
period) along with lack of control over the binge-eating
episode.
➤ Binge-eating disorders are characterized by eating behaviors such as eating rapidly, eating until becoming uncomfortably full, eating large amounts when not hungry, eating
alone because of embarrassment, and disgust, depression,
or guilt because of eating episodes.
and excessive self-evaluation of weight and shape are common to both disorders, and persons with eating disorders
may demonstrate a mixture of both disorders.60 The female
athlete triad, which includes disordered eating, amenorrhea, and osteoporosis, does not meet the strict DSM-IV criteria for anorexia nervosa or bulimia nervosa, but shares
many of the characteristics and therapeutic concerns of the
two disorders (see Chapter 58). Persons with eating disorders may require concomitant evaluation for psychiatric
illness because eating disorders often are accompanied by
mood, anxiety, and personality disorders. Suicidal behavior
may accompany anorexia nervosa and bulimia nervosa and
should be ruled out.57
Anorexia Nervosa
Anorexia nervosa was first described in the scientific literature more than 100 years ago by Sir William Gull.61 The
DSM-IV-TR diagnostic criteria for anorexia nervosa are
(1) a refusal to maintain a minimally normal body weight
for age and height (e.g., at least 85% of minimal expected
weight or BMI of at least 17.5); (2) an intense fear of gaining weight or becoming fat; (3) a disturbance in the way
one’s body size, weight, and shape are perceived; and
(4) amenorrhea (in girls and women after menarche).60
Anorexia nervosa is more prevalent among young women
than men. The disorder typically begins in teenaged girls
who are obese or perceive themselves as being obese.
An interest in weight reduction becomes an obsession,
with severely restricted caloric intake and frequently with
236
UNIT III
Integrative Body Functions
excessive physical exercise. The term anorexia, meaning
“loss of appetite,” is a misnomer because hunger is felt, but
in this case is denied.
Many organ systems are affected by the malnutrition
that occurs in persons with anorexia nervosa. The severity
of the abnormalities tends to be related to the degree of
malnutrition and is reversed by refeeding. The most frequent complication of anorexia is amenorrhea and loss of
secondary sex characteristics with decreased levels of estrogen, which can eventually lead to osteoporosis. Bone
loss can occur in young women after as short a period of
illness as 6 months.57 Symptomatic compression fractures
and kyphosis have been reported. Constipation, cold intolerance and failure to shiver in cold, bradycardia, hypotension, decreased heart size, electrocardiographic changes,
blood and electrolyte abnormalities, and skin with lanugo
(i.e., increased amounts of fine hair) are common. Unexpected sudden deaths have been reported; the risk appears to increase as weight drops to less than 35% to 40%
of ideal weight. It is believed that these deaths are caused
by myocardial degeneration and heart failure rather than
dysrhythmias.
The most exasperating aspect of the treatment of anorexia is the inability of the person with anorexia to recognize there is a problem. Because anorexia is a form of
starvation, it can lead to death if left untreated. A multidisciplinary approach appears to be the most effective
method of treating persons with the disorder.62,63 The goals
of treatment are eating and weight gain, resolution of issues
with the family, healing of pain from the past, and efforts to
work on psychological, relationship, and emotional issues.
tic and diuretic abuse.57,64–66 Among the complications of
self-induced vomiting are dental disorders, parotitis, and
fluid and electrolyte disorders. Dental abnormalities, such
as sensitive teeth, increased dental caries, and periodontal
disease, occur with frequent vomiting because the high
acid content of the vomitus causes tooth enamel to dissolve. Esophagitis, dysphagia, and esophageal stricture are
common. With frequent vomiting, there often is reflux of
gastric contents into the lower esophagus because of relaxation of the lower esophageal sphincter. Vomiting may
lead to aspiration pneumonia, especially in intoxicated or
debilitated persons. Potassium, chloride, and hydrogen are
lost in the vomitus, and frequent vomiting predisposes to
metabolic acidosis with hypokalemia (see Chapter 34). An
unexplained physical response to vomiting is the development of benign, painless parotid gland enlargement.
The weight of persons with bulimia nervosa may fluctuate, although not to the dangerously low levels seen in
anorexia nervosa. Their thoughts and feelings range from
fear of not being able to stop eating to a concern about
gaining too much weight. They also experience feelings of
sadness, anger, guilt, shame, and low self-esteem.
Treatment strategies include psychological and pharmacologic treatments. Unlike persons with anorexia nervosa, persons with bulimia nervosa or binge eating are
upset by the behaviors practiced and the thoughts and
feelings experienced, and they are more willing to accept
help. Pharmacotherapeutic agents include the tricyclic
antidepressants (e.g., desipramine, imipramine), the selective serotonin reuptake inhibitors (e.g., fluoxetine), and
other antidepressant medications.54
Bulimia Nervosa and Binge Eating
Binge Eating. Binge eating is characterized by recurrent
episodes of binge eating at least 2 days per week for
6 months and at least three of the following: (1) eating
rapidly; (2) eating until becoming uncomfortably full;
(3) eating large amounts when not hungry; (4) eating alone
because of embarrassment; and (5) disgust, depression, or
guilt because of eating episodes.57,62,64 Most persons with
binge-eating disorder are overweight, and in turn, obese
persons have a higher prevalence of binge-eating disorder
than the nonobese population.66
The primary goal of therapy for binge-eating disorders
is to establish a regular, healthful eating pattern. Persons
with binge-eating disorders who have been successfully
treated for their eating disorder have reported that making
meal plans, eating a balanced diet at three regular meals a
day, avoiding high-sugar foods and other binge foods,
recording food intake and binge-eating episodes, exercising regularly, finding alternative activities, and avoiding
alcohol and drugs are helpful in maintaining their more
healthful eating behaviors after treatment.
Bulimia nervosa and binge eating are eating disorders that
encompass an array of distinctive behaviors, feelings, and
thoughts. Binge eating is characterized by the consumption of an unusually large quantity of food during a discrete time (e.g., within any 2-hour period) along with lack
of control over the binge-eating episode. A binge-eating/
purging subtype of anorexia nervosa also exists.60 Low body
weight is the major factor that differentiates this subtype
of anorexia nervosa from bulimia nervosa.
Bulimia Nervosa. Bulimia nervosa is 10 times more common in women than men; it usually begins between 13 and
20 years of age and affects up to 3% of young women.64 The
DSM-IV-TR criteria for bulimia nervosa are (1) recurrent
binge eating (at least two times per week for 3 months);
(2) inappropriate compensatory behaviors such as selfinduced vomiting, abuse of laxatives or diuretics, fasting,
or excessive exercise that follow the binge-eating episode;
(3) self-evaluation that is unduly influenced by body shape
and weight; and (4) a determination that the eating disorder
does not occur exclusively during episodes of anorexia nervosa.60 The diagnostic criteria for bulimia nervosa now include subtypes to distinguish patients who compensate by
purging (e.g., vomiting or abuse of laxatives or diuretics)
and those who use nonpurging behaviors (e.g., fasting or
excessive exercise). The disorder may be associated with
other psychiatric disorders, such as substance abuse.57,64,65
The complications of bulimia nervosa include those resulting from overeating, self-induced vomiting, and cathar-
Undernutrition can range from a selective deficiency of a single nutrient to starvation in which there is deprivation of all ingested nutrients. Malnutrition and starvation are among the
most widespread causes of morbidity and mortality in the
world. The body adapts to starvation through the use of fat
stores and glucose synthesis to supply the energy needs of the
central nervous system. Malnutrition is common during illness,
recovery from trauma, and hospitalization. The effects of mal-
CHAPTER 11
nutrition and starvation on body function are widespread.
They include loss of muscle mass, impaired wound healing,
impaired immunologic function, decreased appetite, loss of
calcium and phosphate from bone, anovulation and amenorrhea in women, and decreased testicular function in men.
Anorexia nervosa, bulimia nervosa, and binge eating are
eating disorders that result in malnutrition. In anorexia nervosa, distorted attitudes about eating lead to serious weight
loss and malnutrition. Bulimia nervosa is characterized by secretive episodes or binges of eating large quantities of easily
consumed, high-calorie foods, followed by compensatory behaviors such as fasting, self-induced vomiting, or abuse of
laxatives or diuretics. Binge-eating disorder is characterized by
eating large quantities of food but is not accompanied by
purging and other inappropriate compensatory behaviors
seen in persons with bulimia nervosa.
4.
5.
6.
7.
8.
REVIEW EXERCISES
A 25-year-old woman is 65 inches tall and weighs
300 pounds. She works as a receptionist in an office,
brings her lunch to work with her, spends her evenings
watching television, and gets very little exercise. She reports that she has been fat ever since she was a little girl,
she has tried “every diet under the sun,” and when she
diets she loses some weight, but gains it all back again.
9.
10.
11.
12.
A. Calculate her BMI.
B. How would you classify her obesity?
C. What are her risk factors for obesity?
13.
D. What would be one of the first steps in helping her
develop a plan to lose weight?
A 16-year-old high school student is brought into the
physician’s office by her mother, who is worried because
her daughter insists on dieting because she thinks
she’s too fat. The daughter is 67 inches tall and weighs
96 pounds. Her history reveals that she is a straight-A
student, plays in the orchestra, and is on the track team.
Although she had been having regular menstrual periods, she has not had a period in 4 months. She is given
a tentative diagnosis of anorexia nervosa.
A. What are the diagnostic criteria for a diagnosis of
anorexia nervosa?
14.
15.
16.
17.
B. What is the physiologic reason for her amenorrhea?
C. What are some of the physiologic manifestations associated with malnutrition and severe weight loss?
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