Body Composition:
Its Measurement and Relationship to Health
Overview
In the CrossFit article I didn’t want to get into too much detail on why measuring body
composition doesn’t really work and it is not the forum to post a page of references. So
we added a link to this page (obviously) for those that wanted more information.
I will only briefly mention the most common assessment systems you are likely to
encounter. If you would like some information on other systems please e-mail me (my email address is at the bottom of the CrossFit Journal article). I will also discuss some
common misconceptions about the popular measures of per cent body fat and the body
mass index (BMI) measures. The bottom line is that it is extremely difficult to accurately
measure body composition. In fact there is no totally accurate system and even the best
measurement systems have considerable uncertainty.
Be aware that some measurement systems that are used as measures of body
composition do not assess composition. The body mass index (BMI) is a classic
example, and even university textbooks refer to the BMI as a “rough measure of body
composition”. It isn’t. The BMI has a role to play for epidemiologists and health officials
who are tracking population trends in obesity. However, the BMI on its own is not a
good tool for individual assessment. It is very important that you understand that an
assessment system useful for looking at relationships within the population is not
necessarily useful (and sometimes misleading) for individuals.
Health and Obesity
The negative health consequences of obesity are well documented in the literature and
popular media. However, whether it is just being obese that is the problem, or whether it
is the lifestyle that leads to many North Americans being obese, is a matter of some
debate. I will discuss these issues after I focus on technical non-controversial issues
surrounding body composition. I will also discuss the role that body composition plays
in the health of an individual later.
Percent Body Fat
The fitness industry and most university texts I read in this area identify percent body fat
as the most important consideration when looking at body composition. I would tend to
disagree with an overemphasis on body fat, as percentage (and amount) of lean tissue
and bone density is also very important. If you have a healthy cardiovascular system,
strong musculature and healthy bones your percentage of body fat may not be a health
concern.
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Furthermore, most individuals do not have a clear understanding of percent body fat nor
how difficult it is to measure. On that first point, many females would not be happy to
learn that they had 25% body fat after getting their body fat estimated. However, for a
20-24 year-old female this would be slightly less than average (27%). And the accuracy
of any measurement system is such that you would never be able to determine what
percent body fat you were with any good degree of accuracy. I would say plus or minus
4-6% might be more realistic even with good methods. Some other methods are so
inaccurate as to be a complete waste of time and money.
Another problem with percent body fat estimates occurs when individuals just diet in an
attempt to loose body fat. Although they may be successful, they will also loose a
considerable amount of muscle tissue as well. In this case your percentage of body fat
may not go down and may even increase. This is because your overall body weight has
gone down by loss of both fat and muscle. A better understanding of percentages would
help many people in understanding the unsuitability of this measure.
Below are two graphs of body composition ranges.
Percent Body Fat Classifications
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Age-Height-Weight Tables
Height-for-weight tables have been around for a long time. They are used by insurance
companies but they are not good measures of body composition. However, the history
and flaws behind these tables help us to understand some of the thinking behind body
weight being considered a health risk.
Desirable weight is predicted from tables that have been developed by insurance
actuaries. The tables published by Metropolitan Life Insurance Company in 1983 used
combined data from 25 insurance companies that followed more than four million
policyholders for between one and 22 years. The tables were developed before this
date and have been updated since but it is only important that you realise the influence
of, and the thinking behind these tables rather than focussing on the data.
The tables show the range of weights that were associated with the lowest mortality
rates among the policyholders. Thus, these tables show "desirable" weights, not
"average" weights. The major advantage of these tables is that they are convenient to
use and work for large populations. After all, insurance companies want to assess the
risk for the majority of their policyholders. If a few individuals who are heavily muscled
get inaccurately classified as a health risk, well that is unfortunate for those individuals
but not for the insurance company. I have deliberately not included such tables in this
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document as they are not an accurate assessment of health risk. The main problems
with these tables are:
•
•
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Height-for-weight tables do not consider body composition, as they don't
distinguish between fat and other tissues such as muscle and bone. Body weight
doesn't always reflect obesity, which is a measure of body fatness. Muscular
athletes, for example, may have higher than “normal weight” and still have low
percent body fat.
Most of the data in the Metropolitan weight tables comes from white, middleclass, U.S. males. This is not a representative sample of the general North
American population. The tables apply to people aged 25 to 59 and therefore
don't cover younger adults or the growing number of people over 60.
Many height-weight tables that include frame size as a classification variable do
not specify what criteria to use to determine frame size.
Nevertheless, the simple relationship between mortality rates and height-for-weight has
been a major factor that has led the medical profession to classify obesity as a health
risk. I say simple relationship because in compiling these tables, no attempt has been
made to assess other factors that may be the cause of higher mortality rates.
Body Mass Index
The BMI is calculated by the following equation:
BMI = Weight (kg) / Height (m)2
No matter how you package it this is a height-for-weight measure and is not an
assessment of body composition. Government agencies and researchers find this tool
very useful because you can easily and cheaply get BMI’s of thousands of subjects. If
you have such large numbers of subjects in your studies you can be sure that the vast
majority of those with BMI’s over 25 are overweight because they are “over-fat”. In this
population sample there would be very few individuals with BMI’s over 25 who have a
larger than average amount of muscle. So if you were tracking population BMI’s and
saw an increase, you could quite accurately conclude that the population was getting
fatter. This is in fact exactly what government and health researchers have done, and
have concluded that …… our population is getting fatter! Current U.S. Centre for
Disease Control and Prevention estimates are that 61 percent of Americans are
overweight and 26 percent are obese, or grossly overweight. These figures mean that
the United States leads the world in percent of population that are overweight and/or
obese. We should not be complacent in Canada as we too have a high percentage of
over-fat and obese individuals.
So the BMI is an excellent tool for some applications but not for all. For the individual it
is not a good way of assessing body composition. Although the unfortunate fact is that
the majority of our population is not doing aerobic exercise and resistance training, some
people are, and those who emphasise resistance training often have high BMI’s. It is not
unusual to see professional body builders, boxers and football players with BMI’s over
30. It would be an unscientific, inaccurate and very foolish to label them as obese! Mike
Tyson, the heavyweight boxer, was 180 cm tall and weighed 100 kg when he was in top
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physical condition. This gives him a BMI of 31 and if want to suggest he is obese, go
ahead, I won’t join you. The reason for the high BMI in these individuals is a large
percentage of muscle and higher bone density, not higher fat levels.
Another area for concern is if an individual has a very low BMI score. A very low BMI
score can be associated with individuals who do a large volume of weight bearing
aerobic exercise such as marathon running. However, a low BMI could be due to poor
eating habits and even anorexia nervosa (an eating disorder). Individuals with anorexia
have dangerously low body fat and very low musculoskeletal development. The
assessment of such disorder should be left to qualified health professionals, which is
why I will not discuss this in any detail. Tables showing ideal BMI levels simply list a
BMI score of less than 18.5 and being underweight. The table below shows the
calcification corresponding to various BMI’s but be careful how you use the BMI (as
discussed above).
BMI Key
< 18.5
underweight
18.5 to 24.9
healthy
25 to 29.9
overweight
30 to 34.9
grade 1 obesity
35 to 39.9
grade 2 obesity
>40
grade 3 (morbid obesity)
The link below will take you to a page where you can calculate your BMI….but what
does it tell you the individual?
 http://www.exrx.net/Calculators/BMI.html
Skinfold Measurements
A special calliper is used to measure the
thickness of a double layer of skin and
subcutaneous fat. There are two ways to
use skinfold measurements. The first way
is to add the scores from the various
measurements and use this value as an
indication of the relative degree of fatness
among subjects. The second way to use
skinfold measurements is in conjunction
with equations that have been developed to
predict percent body fat. A large number of
formulas for determining percent fat from
various skinfold measures have been
developed. All of these equations are population specific in that they are more accurate
when they are used with samples of subjects similar in age, sex, fatness and state of
training. When using skinfold measurements to measure percentage body fat, the
person taking the measurements should have considerable experience with the proper
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techniques in order to obtain consistent skinfold measurements, otherwise, considerable
error can be introduced into the estimation of percent body fat. Many experts
recommend just using the skinfold measures and not trying to calculate a percentage
body fat.
The good thing about skinfold measurements is that it is real data collected directly from
the subject. If taken properly it is a good estimate of the amount of subcutaneous fat (fat
located under the skin) in the region of the calliper measure. If skinfolds from enough
sites are taken then you can make a pretty good estimate at the level of subcutaneous
fat the subject has (5 to 8 sites are recommended). However, subcutaneous fat is not
necessarily a good indicator of total body fat and, as discussed in the next section, it is
deep lying fat in the torso that is most associated with health problems (especially
coronary heart disease).
Waist Girth and Hip-to-Waist Ratio
Females tend to have a large proportion to their fat in the breasts and gluteal-femoral
region (buttocks and thighs). This fat is termed “essential fat”, as it is essential for their
reproductive capacity. This patterning is hormonally determined by estrogens and is not
associated with negative health consequences. This pattern of fat deposits is also quite
resistant to dieting and exercise.
The most “risky” fat on the other hand is the non-essential visceral adipose tissue (fat
deposited deep in the abdomen). This type of fat deposition is associated with type 2
diabetes, coronary heart disease and hypertension. It is readily mobilised by energy
demand and is due to hormonally determined androgens. Therefore this type of fat
pattern is far more common in men and post-menopausal woman.
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If you look at the pictures of the two MRI’s abvoe (courtesy Dr. Bob Ross, Queen’s
University, Kingston, Ontario) you will see the problem with just taking skinfolds. The
subject on the left would have high skinfolds in the torso compared with the subject on
the right. However both of these individuals have the same waist circumference (111.0
cm versus 111.7 cm). So in fact, it is the subject on the right who is carrying more
“dangerous” fat deep in his torso, despite having lower skinfold measurements.
These MRI’s highlight the problems with skinfolds alone and show why a combination of
measures such as skinfolds and waist circumference is better. Of course even MRI only
shows body composition at the level of the image….and they are very expensive.
Many health experts think that the waist-to-hip ratios or waist girths alone are very good
indicators of health risk. For men health risks increase if the waist-to-hip ratio is above
0.9 and for women if it is above 0.8. Optimal waist girths vary slightly with age but
generally, health risks increase with waist circumferences above 40 inches for men and
35 inches for women. But as seen in the MRI even waist girth doesn’t prove there is a
high level of fat deep in the torso.
 http://www.exrx.net/Calculators/WaistHipRatio.html
Volume Displacement & Underwater Weighing
As fat tissue is less dense than bone and muscle underwater weighing methods have
attempted to calculate the percentage of fat in the body by measuring and estimating
tissue densities. Underwater weighing can be used to determine the whole body density
of a human by a water displacement" procedure or an "underwater weighing" procedure.
For those into the physics of these techniques, underwater weighing uses Archimedes'
Principle, which states that "an object immersed in a fluid loses an amount of weight
equivalent to the weight of the fluid that is displaced", to determine the volume of a
subject's body. The volume can be measured directly in the volume displacement
method.
The density of a subject's body can then be determined using the following equations:
Density =
Mass
Volume
or
Specific Gravity =
Weight in air
Weight in air - Weight in water
Knowing the density of the whole body is only a first step. The fat in the body has a
known specific gravity (0.9), but we have to assume the density of the lean body mass is
fixed (usually at a specific gravity of 1.1). A simple equation that incorporates density is
then used to determine the relative percentage of fat in the subject's body. The problem
with this is that there are differences in the densities and/or proportion of those tissues
comprising the lean body mass. For example if you have lots of muscle (which has a
specific gravity just over 1) the specific gravity of you fat-free mass will be less than 1.1.
On the other hand if you have healthy dense boned but low muscle mass (a distance
runner may fit this example) then you fat-free mass may have a specific gravity above
1.1. So the theoretical premise that the densities fat-free tissues remain relatively
constant among individuals is flawed. This can lead to the equations predicting that
male professional body builders, who have immense quantities of muscle, have negative
percent body fat! I think we can all see that this can't be correct as it is clearly
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impossible for the percent body fat to be negative. Males need about 3-5% body fat to
live and essential fat levels in females are around 8-12%. These methods are quite
accurate for an average individual (if you know who is average) but the standard
equations used to estimate relative body fat from whole body density are not appropriate
for all segments of the population.
This method of determining percent body fat has historically been considered the most
accurate method. It is the reference method against which many other methods are
compared. For example the equations that are used to predict percent body fat from
skinfold measures are validated against underwater weighing. So if you have a source
of error in your "standard" measurement you can never be accurate when predicting to
this standard from another technique.
Bioelectrical Impedance Analysis (BIA) and Other Techniques
Electrical impedance units are used to measure the electrical resistance of the body.
These units detect changes in electrolyte levels and work on the principle that lean
tissue has far greater electrolyte content than fat. Usually four electrodes are attached
to the subject. The less electrical resistance measured, the more lean tissue a person
has and by inference the less fat.
Many people in the health industry suggest that BIA is as accurate as skinfold
measurements but I have already suggested that using the skinfolds in an equation to
determine percent body fat is not recommended. A number of studies using various
types of subjects have shown percent body fat to be either overestimated or
underestimated using BIA, probably due to variations in body water levels.
There are many other methods I have not discussed. Laboratory methods such as
computed tomography, the Bod Pod, neutron activation, whole body counting of
potassium-40, and isotope dilution are more accurate but are expensive, cumbersome,
and require sensitive equipment and highly trained technicians. These procedures are
usually used for research purposes and are not readily available to the general
population. I am not going to discuss these methods, as they are less common and
either too expensive or too inaccurate to be considered worthwhile for the general
population.
DXA (Dual energy X-ray absorptiometry)
DXA is used in the medical field to assess bone density. Two X-ray beams with differing
energy levels are aimed at the patient's bones. When soft tissue absorption is subtracted
out, the BMD can be determined from the absorption of each beam by bone. Recently
DXA has been used to predict total body composition.
To be honest I have not read a lot of research studies looking at the accuracy of using
DXA to assess soft tissue density. It may be a reasonably accurate system compared to
others. However, the company that sells these assessments in Vancouver do not give a
standard error of estimate. Their “sample” analysis gives percent body fat to one
decimal place! Call me cynical, but I would strongly suggest that they would be lucky to
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have accuracy as food as plus or minus 2% (probably higher). The literature I have read
may conclude that DXA provides valid estimates of body fat, but the word estimate is
always there. And some of the studies compared it to underwater weighing. You can’t
validate a system against a flawed system.
So What Else is there to Assess Body Composition?
Because no single body composition tool is ideal the best scenario is to use a
combination. The Canadian Society for Exercise Physiology uses the BMI in conjunction
with five skinfolds and waist girth. If the BMI and skinfolds are high you can be more
confident that the cause of a high BMI is due to an excess of fat. If on the other hand
the BMI is high and the skinfolds are normal or low then the high BMI is due to greater
than normal musculoskeletal development. The waist girth is then used in conjunction
with the skinfold scores from sites on the torso to assess whether there is a high level of
non-essential visceral adipose tissue.
A Final Word on Body Composition and Percent Body Fat
Ultimately the only accurate method to measure your percent body fat is to cut up your
cadaver and extract all the body fat using chemicals. So do you really want to know
your percent body fat accurately? I think I'll just eat healthily and get some regular
exercise than you very much!
Body Composition as a Health Problem
I would like to discuss some very interesting research in the area of obesity and health.
When it comes to the negative health consequences related to body composition there is
considerable disagreement. There is no end of data telling you obesity is a health
problem. So read these notes as contrary view on this topic.
I have provided references to support the arguments of the research discussed in these
notes at the end of the article. A numbered list of references is towards the back of this
document and the relevant study numbers are within the body of the text. I will be fairly
brief here rather than going into too much detail.
There is no doubt that there is a high correlation between obesity and many negative
health consequences. A large body of epidemiological data has been documented
about the association between obesity and numerous adverse health consequences
including a spectrum of metabolic and cardiovascular disorders. You will have no doubt
read somewhere that obesity is one of the risk factors for developing coronary heart
disease. But correlation is not causation and there is an emerging set of research that
questions the designation of “obesity” as a health risk (1). Increasing evidence suggests
that obesity is not “the health problem” but that factors such as poor diets, inactive
lifestyle, weight cycling (yo-yo weight loss), and possibly weight loss itself are. In other
words, if you are active, eat well and maintain a relatively stable body weight, your body
composition is not a critical factor that will affect your physical health.
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A recent study showed that people with relatively high levels of body fat who exercised
regularly had less health risks that a similar group of individuals who were thin and did
not exercises (2). In this study obese people who exercised had half the death rate of
those who are trim but didn't exercise. Steven Blair, director of research at the Cooper
Institute for Aerobics Research in Dallas argues that previous studies linking obesity and
death from heart disease and other major killers have missed the important influence of
exercise. Blair argues that: "there is a misdirected obsession with weight and weight
loss. The focus is all wrong. It's fitness that is the key." While I have been echoing
similar sentiments for over a decade know I would actually prefer that he said fitness and
diet are the keys.
Studies Blair has conducted involved 25,000 middle-aged men and about 8,000 women
who were followed for 10 years. Fitness was measured by a standard exercise stress
test recording how long people could walk on a treadmill at increasing intensity before
becoming exhausted. The bottom 20 percent of the group was considered unfit. The
findings were the same whether obesity was measured by a body mass index or by the
percentage of body fat relative to muscle and bone, which meant the results were not
due to heavy people simply being well muscled.
Blair emphasises that being fit doesn't eliminate the risk of everything, but rather that you
can stay overweight and possibly actually obese if you are fit and be just as healthy, in
terms of mortality risk, as a lean fit people. Blair has also looked at more than mortality
rates associated with heart disease. He has also looked at other disease rates,
particularly diabetes. The phenomenon holds there too that obese individuals who are fit
develop diabetes at about the same rate as lean individuals who are unfit.
Is Body Composition a Component of Fitness?
Other components of fitness relate to a physiological function.
Aerobic
(cardiorespiratory fitness) ability refers to the ability of the body to deliver oxygen and
nutrients to the working muscles. Muscular strength and endurance is affected by the
performance of muscular contractions. Flexibility is affected by the elasticity of the
connective tissue and muscle surrounding a joint in addition to the joint architecture.
Body composition however, is really an anatomical snapshot of the body. It is related to
anatomy, while the other components are related to physiology. Obviously we see many
obese people who transport fats inefficiently in the bloodstream (in LDL and VLDL
lipoproteins) and as such there are physiological correlates with body composition. But
a healthy diet and a regular exercise regime will greatly improve blood lipid profiles,
irrespective of body composition.
The medical profession is still generally of the option that it is obesity per se that is the
problem. If for example a doctor is counselling an obese patient with normal ECG (heart
electrical activity), blood pressure and blood lipid profile they will still recommend weight
loss. Why? What physiological factors would warrant this advice in such a case? I
suggest it is that epidemiological evidence from large populations has caused some
misconceptions. If you study 10,000 obese North Americans how many of these would
have a healthy diet and exercise regularly? Not many I would imagine and this is the
root of the problem. Is the evidence overwhelming that it is the percent body fat in the
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body that is causing the problems or could it be some other factor? One of the
textbooks I use at my university states “If they [most people] consistently maintain a
wellness lifestyle that includes a healthy diet and regular exercise, the right body
composition will naturally develop”.
Research published in the New England Journal of Medicine in 1995 reported that
women as little as 5 to 10% overweight had a 30 percent increase in risk of heart
disease. This is not much above ideal and many would argue that this amount of
"excess" weight is not a concern. Some argue that a moderate amount of excess weight
can provide you with reserves of energy in times of illness. So why this higher heart
disease rate?
As stated, an emerging body of evidence suggests that one reason for the above results
and indeed the general link between obesity and health risks statistics could be the
effect of weight cycling (see below). Ernsberger and Koletsky (3) have induced high
blood pressure in animals by forcing them to consuming diets that made them gain and
loose weight in a cyclic manner. Studies of zoo animals showed no correlation between
obesity and hypertension (high blood pressure) and Ernsberger and others have
suggested that this is because these animals tend to maintain a stable body weight.
Other studies have linked diet pills with damage to heart muscle. Another factor that
could contribute to the correlation between health and obesity is the psychological stress
that being obese in our society can cause. Such stress can cause many health
problems. In societies where obesity is not treated with such disdain, obese individuals
appear to have less health problems.
This is a very difficult area and one that I have done some reading in, but not enough to
claim to be an expert. For now I think it prudent for me to suggest you eat a healthy diet
and get regular exercise. If these two regimes are followed your body composition
should be considered to be normal for you. Intervention to alter your body composition,
even though you are exercising regularly and eating sensibly, is not only unlikely to be
successful, but in addition, some researchers claim it may be dangerous.
Weight Cycling
It is possible that the increased mortality rates associated with weight loss are
contributed to by weight cycling and not necessarily weight loss itself. Obese humans
frequently alternate between caloric restriction and bingeing and show repeated cycles
of weight loss and regain (4,5,6). These fluctuations of body weight have been shown in
several major epidemiological studies to have deleterious cardiovascular effects
resulting in increased mortality (3,7,8,9). Several epidemiological studies revealed
higher all-cause (primarily from cardiovascular disease) death rates among men and
women who had experienced considerable weight fluctuations (8,10). The higher death
rates may reflect elevated blood pressure that has been documented to occur during
repeated cycles of weight loss and regain (11,12,13,14).
The increased mortality and morbidity associated with weight cycling in humans is
supported by a number of animal models but I will not go into any further detail. Studies
on mice, rats, swine, and dogs, have reported that weight cycling induces many
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disorders including, hypertension, vascular damage, and increased plasma insulin levels
among other problems.
Academic honesty means that I cannot only present only one view of weight cycling.
Scientists from the Harvard School of Public Health have found that at least in terms of
high blood pressure, which is a major risk factor for heart disease, weight cycling,
doesn’t carry the risk some other studies have reported (15). They questioned some
48,000 women on their dieting habits and then followed the group to see whether they
developed high blood pressure. During the four-year study period, nearly 80 percent of
the women lost weight at least once. Twenty percent of them lost and regained 10
pounds three times or more. A smaller number lost 20-plus pounds many times. That’s
important because blood pressure is very sensitive to changes in weight: even when you
gain or lose as few as 10 pounds your blood pressure can go up or down accordingly.
By the end of the study about 1,100 of the women did, in fact, develop high blood
pressure. But their shifts in weight didn’t appear to add an extra element of risk. That is,
high blood pressure was not associated with the number of times the women had lost
and regained weight. Rather, it corresponded with their net weight gain: for 10 pounds a
women put on over the four-year study, her risk of high pressure went up 20 percent.
For example, if she lost and regained the same 30 pounds, her blood pressure risk was
no different, but if she lost 30 pounds and regained 40 pounds, her risk increased (15).
So this study might not prove that weight cycling is harmless but rather that the danger
of rebounding to a higher weight is the bigger risk. I would note that this study is
dependent on questionnaire data that is prone to error.
Physical Inactivity, Low Fitness Levels and Diet
I have already touched on this but will provide a few more references here. Many
studies suggest that behavioural factors are more important than body weight as
determinants of blood pressure. These studies have shown that overweight/obesityrelated problems such as hypertension, high blood lipid levels, insulin resistance, and
glucose intolerance can be improved independently of weight loss (16). For example the
Dietary Approaches to Stop Hypertension Trial, demonstrated that blood pressures
could be effectively lowered with simple changes in diet in the absence of weight loss
(17).
Reduction in blood pressure appears not to be due to the reductions in body fat but
rather appears to be more strongly linked to decreases in plasma insulin (16).
Therefore, reductions in body fat via exercise are not necessary for improving insulin
sensitivity. Many studies have confirmed that while weight loss does occur with
combined exercise and diet intervention; it appears that exercise is more important
than weight loss itself for improving insulin sensitivity (16). This is borne out by the
data that I have presented earlier showing obese fit individuals having no greater risk of
diabetes that thin unfit individuals (2).
Other studies suggest that the quality of diet is more important than weight loss for
improving serum lipid and lipoprotein profile. Among 4587 men and women who
underwent a 3-week, residential lifestyle modification program emphasising aerobic
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exercise and healthy eating, less than 3% of the reduction in serum total cholesterol,
LDL-C and triglycerides could be explained by reduction in bodyweight (16).
In a Cholesterol Lowering Atherosclerosis Study (18), modest reductions in dietary fat
intake among moderately overweight men with heart disease prevented the formation of
new atherosclerotic lesions (damaging heart blood vessels) during a 2-year-trial. This
occurred in the absence of weight loss.
Stress and Body Image
It has long been known that individuals who experience high levels of stress are at
greater risk of coronary heart disease among other health problems. This connection
between stress and cardiovascular disease has a body image link for some. Our society
focuses on thinness as being desirable and for those individuals who are genetically
prone to being overweight this can be very stressful. There is evidence that our society
discriminates against obese individuals, which adds to this stress. Therefore it is
possible that the issue of psychological stress also confounds the relationship between
obesity and negative health consequence.
Prescription Drugs
Diet pills can be temporarily effective in weight loss but can pose a health risk. Consider
the amount of epidemiological evidence that links obesity to increased heart disease
risk. However, two weight loss drugs were removed from the market in 1997 as they
were linked to heart valve problems. Some experts argue that by the time you factor in
the risks of weight cycling, poor diets and drug use that the correlation between obesity
and coronary heart disease would be a lot weaker if even there at all.
Problems with, and the Reporting of Research?
Some researchers suggest there is a problem with a lot of the epidemiological research
conducted in this area. Cross-sectional surveys where you look at the incidence of
variables at one point in time are the weakest type of medical study. Although more time
consuming, you would rather follow people over a longer period of time documenting
lifestyle and health issues. Although cross-sectional studies are the least reliable, and
are usually not considered when other information is available, obesity experts rely
primarily on these health surveys. These cross-sectional studies generally paint a much
more unfavourable picture of the health of obese persons than controlled prospective
studies.
Other researchers highlight problems with the validity of the obesity-health relationship
due to how the data is reported and collected. For example, some suggest that obese
persons may report more medical problems than thinner individuals even if the
incidences of these problems are similar. Another problem is called diagnostic bias as
doctors are trained to expect certain diseases in obese persons and may diagnose them
more readily.
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Another fact is that articles describing obesity as being extremely hazardous are quoted
more extensively in the scholarly literature than equivalent articles drawing more
sceptical conclusions. This is could be argued is due to there being more solid research
showing this negative association between health and obesity. Others however claim
this is selective citation.
For example, Ernsberger and Koletsky found that a
comprehensive critical review of the health risks of obesity with more than 400
references has been cited only 2.3 times per year (11). In contrast, reviews offering
much grimmer assessments of the health of obese persons, composed by the director of
a hospital weight loss clinic, have been cited at an annual rate of 9.2 and 34.7 (19). The
fewer citations of the articles cannot be attributed to lower academic standing because
the lead authors are usually excellent researchers who have published extensively in
major medical journals. This trend can also be seen in media coverage of medical
findings, in which extensive attention is devoted to reports of obesity hazards and scant
attention is paid to the extensive contrary evidence (16).
Another compounding factor is that BMI is used as a measure of obesity in many of the
studies. While I have already stated in the discussion on body composition that this
works for insurance companies and for general estimates of population weight gain, it
could be problematic in scientific studies. The pattern of fat distribution is one of the
most obvious factors that could render results suspect, as fat carried in the torso is much
more likely to be a health risk
I am not an epidemiologist but I hope that I have given you a good argument for a
reconsideration of the prevailing idea that obesity per se is a health risk. There is still
much more research to be done and experts in this field don't know all the answers yet,
but I think the evidence is mounting that one should take care of their diet and activity
profile first, before they consider any other method of weight control.
Weight Control as a Fashion
Ultimately, many individuals, especially females, are going to try to force their body
weight towards an idealistic goal because of factors other than health. A big reason that
smoking hasn’t decreased much in teenage females is that despite the negative health
consequences, smoking is seen as an appetite suppressor and something that can help
control body weight.
A detailed discussion of this issue is outside the scope of this article (and my expertise).
I will leave this topic by saying that if you are exercising regularly and eating a healthy
diet you will reap many of the health benefits already discussed. However, if you try to
force your body weight to a standard that does not fit your natural body type, either by
dieting, excessive exercising or drugs, you run the risk of damaging your health. What
price will you pay for fashion?
The Practical Side of Weight Control
People might still want to shed pounds for some practical reasons like being able to fit
more comfortably into an airline seat. There is no doubt that many things in our society
are not designed for a variety of body types. You only have to talk to left-handed
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individuals to learn that designers design items to fit predominant human features and
those not fitting into the average range just have to make do.
On a darker note, other reasons to loose weight may include trying to stop others
discriminating against you. There is no doubt that “thin is in” and that this trend does
cause considerable distress for many of those whose body type doesn’t fit the ideal
image. Obviously many people are able to ignore such pressures and focus on living a
healthy fulfilling life, but I imagine it can’t be easy for many others. I say I imagine
because I have been thin all my life and must admit that I cannot fully appreciate the
issues obese individuals have to face.
The issue of psychological stress associated with being obese or over-fat are outside of
my area of expertise and the focus of this article. I know more about the physiological
aspects of exercise and health rather than the psychological. I hope that this discussion
can help individuals whose genetic make up predisposes them to having a high percent
of body fat realise that they can be healthy without weight loss.
Other Risks of Obesity
Some experts who agree with the arguments I have put forward here would caution that
reaching an appropriate weight is still advisable for preventing other complications of
obesity that are not thought to be related to fitness, such as cancer, arthritis and
infertility. However, my personal belief is that the majority of individuals who are obese
would loose significant amounts of body fat if they exercised regularly and ate a proper
diet. Many others would drop below obese classifications and although they may remain
slightly over-fat due to genetic predisposition they would not be in a high health risk
range for other diseases. One must accept that even thin and fit individuals carry some
genes that would predispose them to some health risks. Nobody can be free of health
risks completely. In addition, until more research is completed, it is still not clear
whether those individuals whose genetic make-up resists significant fat loss are at
significantly higher risk to other diseases such as cancer. The reason I say this is
because there may be links between diet and cancer that compound the problem. As
we have discussed, the present situation is that the majority of North Americans who are
obese do not exercise eat a diet high in fat and sugar.
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