Composition (lean and fat tissue) of weight changes in adult
Danes1–3
ABSTRACT
Background: Weight loss may be associated with unfavorable
changes in body composition not compensated for by subsequent
weight gain.
Objective: We examined the composition of weight change in
relation to obesity, previous weight changes, weight-loss attempts,
and physical activity.
Design: Part of the Danish MONICA (Monitoring Trends in Cardiovascular Disease) project, this was a longitudinal population
study of changes in weight and body composition, with examinations in 1982–1983, 1987–1988, and 1993–1994. A total of
1236 men and 1200 women aged 35, 45, 55, or 65 y in 1987–1988
participated. Changes in fat and fat-free mass were measured by
bioelectrical impedance.
Results: Before adjustment for age-related changes, fat-free
mass made up 41% of weight lost and 24% of weight gained in
men. In women, loss of fat-free mass (35%) was more than double that of gains (15%). After adjustment, the fractions of weight
gained as fat-free mass were not significantly different from the
fractions lost. These fractions were independent of age, obesity,
and weight changes in the previous 5 y; successful weight-loss
attempts; and physical activity. Independent of age and degree of
obesity, weight changes were associated with greater changes in
fat-free mass in men than in women.
Conclusions: These data do not support the theory that weight
loss or weight cycling may lead to an unfavorable body composition, nor do they provide a biological explanation for why
long-term weight loss is often unsuccessful. However, the metabolic and health consequences of weight change may differ in
men and women.
Am J Clin Nutr 2002;75:840–7.
ratio of body fat to fat-free mass. Such changes are not picked
up by measures of relative overweight, such as the body mass
index (BMI), and may help explain why both weight cycling
and weight loss seem to be related to increased mortality.
Several studies examined this question in experimental and
observational settings (5–10). These studies generally found no
evidence of a difference in gain and loss of fat-free mass with
weight change, but they had limitations: the authors did not
specifically address the question of disproportionate loss and
gain of lean mass (9); data were restricted to small, often highly
physically active groups (7, 8); data were cross sectional in origin (5, 7, 8); or there was insufficient statistical information to
interpret their data (10). We used cross-sectional data in a previous study to examine the composition of body weight differences in large groups of apparently healthy subjects of the same
height and showed that fractions of fat-free mass per differences in body weight (in kg) were 72% and 65% in women
and men, respectively (5). We suggested that these fractions
closely resemble the composition of weight change in comparable groups of subjects.
In the present study we examined the composition of weight
changes in 2436 Danish adults between examinations in
1987–1988 and 1993–1994. Because many factors—age, degree
of obesity, previous weight changes, successful weight-loss
attempts, and physical activity during leisure—may influence
the composition of the weight lost or gained, we investigated
whether weight loss and gain are accompanied by different relative changes in body composition in groups of subjects characterized by differences in these factors.
KEY WORDS
Body composition, obesity, weight change,
longitudinal population study, Denmark, fat-free mass, weight
cycling, Danish MONICA project
1
From the Centre for Preventive Medicine, Unit for Dietary Studies,
Glostrup University Hospital, University of Copenhagen, and the Danish Epidemiology Science Centre at the Institute of Preventive Medicine, Copenhagen, University Hospital (BLH), and the Department of Physiology, University of Odense, Denmark (LG).
2
Supported by The Danish Research Council (FREJA), the Danish Health
Insurance Foundation, The Wedell-Wedellsborgs Foundation, and the Danish
National Research Foundation.
3
Reprints not available. Address correspondence to BL Heitmann, Institute of Preventive Medicine, Copenhagen University Hospital, Øster
Farimagsgade 5A, opg 23A 1399 København K, Denmark. E-mail:
[email protected].
Received September 22, 2000.
Accepted for publication June 15, 2001.
INTRODUCTION
Most studies report that weight loss is associated with
increased mortality (1). In addition, most available studies
suggest that repeated weight loss and gain—so-called weight
cycling—carries an independent health risk (2–4). One hypothesis is that weight loss is associated with an unfavorable change
in body composition that is not compensated for by a subsequent gain in weight, ie, that weight cycling results in a higher
840
Am J Clin Nutr 2002;75:840–7. Printed in USA. © 2002 American Society for Clinical Nutrition
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Berit Lilienthal Heitmann and Lars Garby
COMPOSITION OF WEIGHT CHANGE
841
Weight changes
Subjects
The present study focused on changes in weight and body
composition between the examinations of 1987–1988 and
1993–1994. Body weight changes of ≤ 2 kg were considered to
be normal daily variations. Only a gain or loss of > 3 kg was considered a significant weight change. Subjects with weight
changes of > 2 but < 3 kg were excluded from further study
(n = 229). Weight changes between the examinations in
1982–1983 and 1987–1988 were used only to describe the
grouping variable, weight changes in the previous 5 y. We also
examined the effects of weight change between the 1982–1983
and 1987–1988 examinations on subsequent body composition
changes (gain or loss of > 1 kg was chosen because weight-loss
groups in particular were very small if the cutoff was > 3 kg) and
of whether subjects reported that they had succeeded in an
attempt to lose weight.
The study was part of the Danish MONICA-I (Monitoring
Trends in Cardiovascular Disease) project, an international study
conducted under the auspices of the World Health Organization to
monitor trends in and determinants of mortality from cardiovascular disease (11). The first survey was carried out in 1982–1983. An
age-stratified sample of subjects (n = 4807) aged 30, 40, 50, and
60 y was selected at random from the Central Person Register
from citizens living in 11 municipalities in the western part of
Copenhagen County. Subjects not born in Denmark were excluded
(n = 226). The remaining 4581 subjects were found to be reasonably representative of the total Danish population with respect to
sex, age, educational level, occupation, and housing, but persons
employed in agriculture, horticulture, or fishery and self-employed
and unskilled workers were slightly underrepresented (12). Of the
4581 subjects, 3608 (79%) were given a general health examination, including measurement of height and weight. All of these
subjects who were still living were invited to 2 reexaminations,
one performed between December 1987 and November 1988 (13)
and another between May 1993 and November 1994 (14). A total
of 2987 subjects (83%) aged 35, 45, 55, or 65 y were examined in
1987–1988, and 2656 subjects (74%) aged 41, 51, 61, and 71 y
were examined in 1993–1994. Height and weight were measured
at all 3 examinations, but body composition was measured only in
the latter 2. The population groups and measures were described
in detail elsewhere (13, 14). Complete data from all 3 examinations were obtained for 2436 subjects. All subjects gave written
informed consent. The project was approved by the Ethics Committee for Copenhagen County and is in accordance with the
Helsinki Declaration of 1975 as revised in 1983.
Anthropometric data
All anthropometric measurements were made in accordance
with World Health Organization standards (15). Height was measured to the nearest 0.5 cm while the subjects were standing without shoes, with their heels together, and with their heads in the
horizontal Frankfurter plane. Body weight was measured to the
nearest 0.1 kg on a Seca scale (Copenhagen), with the subjects
wearing only hospital underwear.
Measurements of electrical impedance
We used a BIA-103 body-composition analyzer (RJL Systems,
Detroit) to measure electrical impedance, following the manufacturer’s instructions. Measurements were taken with a tetrapolar
electrode arrangement while the subjects were lying relaxed on a
couch. The electrodes were placed on the dorsal surfaces of the
right hand and foot at the distal metacarpals and metatarsals,
respectively, and between the distal prominence of the radius and
the ulna at the wrist and the medial and lateral malleoli at the ankle.
In a previous study we used a subset of our population to develop
an equation for estimating body fat from impedance, with measurements of total body water and potassium as a reference (16):
BF (kg) = 0.819 BW (kg) 0.279 Ht /R
(cm2/ohm) 0.064 sex BW (kg)
+ 0.077 age (y) 0.231 Ht (cm)
+ 14.941
2
Questionnaire data in 1987–1988
A simple ranking scale for physical activity during leisure was
validated previously and found to perform well in separating
sedentary and more active groups (17). The subjects were asked
to rank their leisure-time level of activity as 1) mostly sitting,
2) light activity ≥ 4 h/wk, 3) active in sport ≥ 3 h/wk or heavy
work during leisure, or 4) active in a competitive sport several
times per week. Few of the subjects fell into the latter category;
therefore, groups 3 and 4 were merged for the present analyses.
The subjects were asked whether they were current or exsmokers or had never smoked. They were also asked whether in the
previous 5 y they had followed a diet through which they had
been successful in losing > 5 kg.
Statistical methods
Analysis of variance was used to evaluate differences between
groups of subjects by sex. Because adults lose fat-free mass with
age (18, 19), we adjusted for age-related changes in body composition with the use of linear regression. For each combination
of sex, weight-change group (loss, gain, or stable), and either age,
percentage body fat, weight change in the previous 5 y, successful weight-loss attempts, or physical activity level, a model
including a set of regression analyses of the change in fat-free
mass relative to the change in body weight (fat-free mass/body
weight) was tested. The estimated slopes in these models describe
the part of the change in body weight that is fat-free mass. The
estimated intercepts to these slopes describe the change in fatfree mass by time. Slopes and intercepts were tested for interactions between the different combinations to examine the differences in gain and loss of fat-free mass with weight changes.
Differences with a P value < 0.05 were considered statistically
significant. The analyses were performed by using SAS statistical
procedures (version 8.0; SAS Institute Inc, Cary, NC).
RESULTS
Nonparticipation
(1)
where BF is body fat, Ht is height, and BW is body weight. Sex
is coded as 1 for men and 0 for women.
The nonparticipants were older than the participants (P < 0.0001).
After adjustment for these age differences, height, weight, and
BMI did not differ significantly at baseline or follow-up between
participants and nonparticipants. Nonparticipation was described
in detail previously (12, 13).
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SUBJECTS AND METHODS
842
HEITMANN AND GARBY
TABLE 1
Subject characteristics and body-composition indexes estimated by electrical impedance for all subjects and for weight-stable, weight-loss, and weightgain groups1
All subjects
Weight stable
Weight group
Weight loss
Weight gain
Men
n
loss or gain of ≤ 2 kg between examinations; weight loss, loss of > 3 kg between examinations; weight gain, gain of > 3 kg between examinations.
2–4
P for trend across groups (ANOVA): 2 P < 0.0001, 3 P < 0.01, 4 P < 0.05.
Changes in body composition related to age
Mean (± SD) characteristics of subjects from the 3 examinations are shown in Table 1 by sex for the total group and by weight
status (ie, stable weight, weight loss > 3 kg, and weight gain > 3 kg)
between the 1987–1988 and 1993–1994 examinations.
Between the 1987–1988 and 1993–1994 examinations, 156
men and 125 women lost > 3 kg and 480 men and 486 women
gained > 3 kg. In 1987–1988 BMI and body fat were greater in
men and women who subsequently lost weight than in those who
gained weight, but fat-free mass did not differ significantly
between the sexes.
Changes in body fat and fat-free mass in subjects whose weight
was stable during the 6-y period reflect the expected loss in fatfree mass and gain in body fat related to age. Before adjustment
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1236
453
156
480
1982–1983
Age (y)
43.9 ± 10.7
45.6 ± 10.3
47.4 ± 10.6
41.6 ± 10.42
Body weight (kg)
78.4 ± 11.3
77.1 ± 10.8
80.3 ± 12.0
79.4 ± 11.4
Body height (cm)
176.2 ± 6.7
175.7 ± 6.7
175.9 ± 6.8
176.9 ± 6.63
BMI (kg/m2)
25.2 ± 3.4
25.0 ± 3.3
26.0 ± 3.8
25.4 ± 3.4
1987–1988
Body weight (kg)
79.8 ± 11.7
78.5 ± 11.3
82.7 ± 13.2
80.6 ± 11.6
25.7 ± 3.5
25.5 ± 3.3
26.8 ± 3.9
25.8 ± 3.43
BMI (kg/m2)
BF (kg)
19.8 ± 7.0
19.2 ± 6.7
22.2 ± 7.9
19.8 ± 6.83
FFM (kg)
60.0 ± 6.1
59.2 ± 5.9
60.5 ± 6.4
60.7 ± 6.13
1993–1994
Body weight (kg)
81.7 ± 12.6
78.7 ± 11.3
76.9 ± 12.7
86.9 ± 12.32
2
BMI (kg/m )
26.5 ± 3.7
25.7 ± 3.4
25.1 ± 3.8
27.9 ± 3.72
BF (kg)
21.3 ± 7.3
19.7 ± 6.6
18.5 ± 7.4
24.2 ± 7.12
FFM (kg)
60.3 ± 6.5
59.0 ± 5.9
58.3 ± 6.6
62.6 ± 6.42
Weight change: 1983–1988
Body weight (kg)
1.4 ± 4.5
1.4 ± 3.8
2.4 ± 4.3
1.2 ± 5.13
Weight change: 1988–1994
Body weight (kg)
1.9 ± 4.7
0.2 ± 1.2
5.8 ± 2.9
6.3 ± 3.12
BF (kg)
1.6 ± 3.3
0.5 ± 1.2
3.5 ± 2.1
4.5 ± 2.32
FFM (kg)
0.3 ± 1.9
0.2 ± 1.1
2.2 ± 1.4
1.9 ± 1.42
Women
n
1200
417
125
486
1982–1983
Age (y)
43.6 ± 10.9
44.7 ± 11.2
47.5 ± 11.5
41.5 ± 10.02
Body weight (kg)
63.3 ± 10.5
61.7 ± 9.4
66.7 ± 12.9
63.9 ± 10.8
Body height (cm)
163.7 ± 6.1
163.7 ± 6.2
162.4 ± 5.7
164.2 ± 6.03
BMI (kg/m2)
23.6 ± 3.8
23.1 ± 3.4
25.3 ± 4.7
23.7 ± 3.9
1987–1988
Body weight (kg)
65.1 ± 11.1
63.7 ± 10.4
69.7 ± 13.3
65.3 ± 11.1
BMI (kg/m2)
24.4 ± 4.1
23.9 ± 3.9
26.5 ± 4.8
24.3 ± 4.0
BF (kg)
21.2 ± 8.2
20.2 ± 7.7
25.6 ± 9.6
21.1 ± 8.04
FFM (kg)
43.8 ± 4.7
43.6 ± 4.6
44.1 ± 5.3
44.2 ± 4.73
1993–1994
Body weight (kg)
67.4 ± 12.1
63.9 ± 10.4
63.8 ± 12.5
71.8 ± 12.52
BMI (kg/m2)
25.3 ± 4.5
24.1 ± 3.9
24.5 ± 4.5
26.8 ± 4.62
BF (kg)
23.4 ± 8.7
20.8 ± 7.8
21.5 ± 8.8
26.5 ± 8.92
FFM (kg)
43.9 ± 5.0
43.1 ± 4.6
42.2 ± 5.3
45.2 ± 5.02
Weight change: 1983–1988
Body weight (kg)
1.8 ± 4.9
2.0 ± 3.6
3.0 ± 5.1
1.4 ± 5.92
Weight change: 1988–1994
Body weight (kg)
2.3 ± 4.9
0.2 ± 1.2
5.9 ± 3.1
6.6 ± 3.72
BF (kg)
2.2 ± 3.9
0.7 ± 1.5
4.1 ± 2.6
5.5 ± 3.12
FFM (kg)
0.1 ± 1.7
0.4 ± 1.3
1.8 ± 1.4
1.1 ± 1.52
1–
x ± SD. Measurements are from 3 examinations; body composition was measured only at the latter 2. BF, body fat; FFM, fat-free mass; weight stable,
COMPOSITION OF WEIGHT CHANGE
TABLE 2
Relative change in fat-free mass as a fraction of body weight in the 3
weight groups1
Weight stable2
Weight loss
Weight gain
Men
0.33 ± 0.02 [453]
0.33 ± 0.01 [156]
0.34 ± 0.01 [480]
Women
0.25 ± 0.03 [417]
0.23 ± 0.01 [125]
0.24 ± 0.01 [486]
1–
x ± SD; n in brackets. Adjustment was made for age-related changes
in body composition, independent of weight changes. Weight stable, loss
or gain of ≤ 2 kg between examinations; weight loss, loss of > 3 kg
between examinations; weight gain, gain of > 3 kg between examinations. There were no significant within-sex differences between groups.
2
Significant interaction of weight group and sex, P < 0.0001 (ANOVA).
FIGURE 1. Mean (± SD) change () in fat-free mass (FFM) as a percentage of the change in body weight (BW) among men (solid lines) and
women (dotted lines) aged 35, 45, 55, or 65 y who gained () or lost ( )
> 3 kg BW between the 1987–1988 and 1993–1994 examinations, before
adjustment for age-related changes in FFM. The changes in FFM were
significantly different with weight loss and weight gain in both sexes
(P < 0.003, ANOVA) and between sexes (P < 0.0001, ANOVA).
significantly different from zero (Figure 2). Differences between
men and women remained, however, and were independent of age
(P = 0.01). The interaction of sex and age was significant both
before and after adjustment (P < 0.0001).
Changes in body composition related to degree of obesity
Men and women were grouped according to quartiles of percentage body fat in 1987–1988. Before adjustment for agerelated changes in body composition, the fraction of fat-free
mass lost with weight loss was greater than the fraction gained
with weight gain, and this difference was greater in the lean than
in the obese persons (all P < 0.003; data not shown). After
adjustment, fractions of fat-free mass gained or lost with weight
changes were not significantly different between the lean and the
obese persons, as indicated by intercepts that were not significantly different and estimated slopes that were not significantly
different from zero. Data are given for men and women separately in Figure 3. Differences between men and women remained
and were independent of percentage body fat (P = 0.01). The
interaction of sex and percentage body fat was significant both
before and after adjustment (P < 0.0001).
Changes in body composition related to amount of physical
activity
The analyses showed that physical activity did not significantly
influence the fractions of body weight changes subsequently
gained or lost as fat-free mass, but that fractions of fat-free mass
lost with weight loss were greater than fractions gained with
weight gain before adjustment for age-related changes in body
composition (both P < 0.0005; data not shown). After adjustment,
the fractions of fat-free mass gained or lost with weight changes
were not significantly different for active and inactive subjects
(Figure 4), as indicated by intercepts that were not significantly
different and estimated slopes that were not significantly different
FIGURE 2. Mean (± SD) change () in fat-free mass (FFM) as a
percentage of the change in body weight (BW) in men (solid lines) and
women (dotted lines) aged 35, 45, 55, or 65 y who gained () or lost ( )
> 3 kg BW between the 1987–1988 and 1993–1994 examinations, after
adjustment for age-related changes in FFM. There were no significant
within-sex differences between groups, but the differences between men
and women were significant (P < 0.0001, ANOVA).
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for these age-related changes in body composition, which are
independent of weight change, the fraction of body weight lost as
fat-free mass was greater than that gained as fat-free mass (men,
41% compared with 24%; women, 35% compared with 15%).
However, after adjustment for age-related changes in body composition, the fractions of body weight lost and gained as fat-free
mass were not significantly different, and these fractions made up
33% of the body weight change in men and 25% of the
weight change in women. The difference between men and
women was significant across all weight groups (Table 2).
Subjects who lost weight were older and subjects who gained
weight were younger than the average (Table 1). Age-related
changes increased with age in both men and women. Before the
adjustment for the age-related changes in body composition, the
fraction of fat-free mass lost with weight loss was greater than the
fraction gained with weight gain, and this difference increased
with age (Figure 1). However, after adjustment, fractions of fatfree mass gained or lost with weight changes were independent of
age for both men and women, as indicated by intercepts that were
not significantly different and estimated slopes that were not
843
844
HEITMANN AND GARBY
from zero. However, the differences between men and women
remained significant and were independent of physical activity
levels. The interaction of sex and physical activity was significant
both before and after adjustment (P < 0.0001).
Changes in body composition related to weight changes in
the previous 5 y and successful weight-loss attempts
Weight changes in the previous 5 y did not significantly influence the fractions of body weight changes subsequently gained
FIGURE 4. Mean (± SD) change () in fat-free mass (FFM) as a percentage of the change in body weight (BW), by physical activity in men
(solid lines) and women (dotted lines) who gained () or lost ( ) > 3 kg
BW between the 1987–1988 and 1993–1994 examinations, adjustment
for age-related changes in FFM. There were no significant within-sex
differences between groups, but the differences between men and
women were significant (P < 0.0001, ANOVA).
or lost as fat-free mass, but the fractions of fat-free mass lost
with weight loss were greater than the fractions gained with
weight gain before the adjustment for age-related changes in
body composition (both P < 0.002). After adjustment, the fractions of fat-free mass gained or lost with weight changes were
not significantly different for subjects with a weight gain or loss
in the previous 5 y (Figure 5), as indicated by intercepts that
were not significantly different and estimated slopes that were
not significantly different from zero. The interaction of sex and
weight change in the previous 5 y was significant both before
and after adjustment (P < 0.0001).
The fraction of fat-free mass lost with weight loss was not
significantly dependent on successful weight-loss attempts,
although the fractions of fat-free mass lost with weight loss
tended to be smaller for intentional losses (Table 3). The interaction of sex and successful weight loss was significant both
before and after adjustment (P < 0.01). However, differences
between men and women remained and were independent of
weight changes in the previous 5 y and of successful weight-loss
attempts (both P < 0.0001).
DISCUSSION
The present study showed that the weight-gaining groups were
younger and the weight-losing groups were older than average, in
agreement with the findings of other studies (13, 20). Hence,
those losing weight would be expected to lose relatively more fatfree mass as a simple consequence of being older. Indeed, it is
well known that changes in body composition that are independent of weight changes vary with age (9, 21), suggesting that a
substantial reorganization of fat and fat-free mass occurs with
aging. The present study agrees with other studies in showing that
age-related losses of fat-free mass, independent of weight
changes, increase with age. However, changes in body composition occurring with weight changes were constant in persons aged
35–70 y, as suggested by the fact that fat-free mass did not make
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FIGURE 3. Mean (± SD) change () in fat-free mass (FFM) as a percentage of the change in body weight (BW), by percentage body fat adjusted for
age, in men (solid lines) and women (dotted lines) who gained () or lost ( ) > 3 kg BW between the 1987–1988 and 1993–1994 examinations, after
adjustment for age-related changes in FFM. There were no significant within-sex differences between groups, but the differences between men and
women were significant (P < 0.0001, ANOVA).
COMPOSITION OF WEIGHT CHANGE
up a greater fraction of weight loss than of weight gain when agerelated changes in body composition were adjusted for. These
findings are in general agreement with results obtained from
experimental and cross-sectional population studies (5–10), even
though the very elderly may show a disproportionally large loss
of fat-free mass in relation to weight loss (18). Data from the
present study on the composition of body weight changes (Table 2)
are almost exactly the same as our cross-sectional data on weight
differences (5). Of particular interest in the present study is the
remarkably small variation among subjects in the composition of
the weight changes, with CVs of only 3–4%.
We found that weight changes were associated with more
unfavorable relative changes in fat-free mass in men than in
women, even after considering age-related changes in fat-free
mass and the differences in percentage body fat between men
and women. This finding agrees with that of our cross-sectional
study (5). However, the finding is surprising because it was
assumed that such sex differences depended on differences in
body fatness and because most, but not all (21), studies failed to
show such differences (22–24). Experimental studies have found
that physical activity decreases losses of fat-free mass (20, 25).
Hence, differences in physical activity provided one speculative
explanation for the differences between the sexes. However, in
the present study more women than men reported being inactive,
and changes in fat-free mass were not significantly different
between those who were physically active and those who were
inactive at baseline (data not shown).
Our results imply that in middle-aged adults, metabolic and
other health consequences of weight change are dependent on sex.
Few studies have had the aim or the statistical power to explore
health differences between men and women related to BMI or
changes in BMI. However, crude data from 1.7 million Norwegian
adults suggest that compared with middle-aged women, middle-
aged men have a greater mortality both at a high and at a low
BMI (26). At later ages these differences seem to disappear.
The finding that the change in fat-free mass relative to the
change in body weight was unrelated to percentage body fat was
also surprising, because others suggested that during weight
change more fat is lost or gained by obese than by lean persons
(9, 21, 24, 27). Although the possibility cannot be excluded that
body-composition changes in subjects who are very lean differ
from those of who are very obese, the results of the present
study, conducted on a large sample of adult Danes with substantial variation in body composition, provide no support for this.
Weight loss may be voluntary or involuntary, and the composition of the weight lost may depend on this. We addressed this
question by examining whether a different fraction of weight lost
was fat-free mass in subjects who reported successful weight-loss
attempts than in those who did not. Although we found no significant difference once age-related changes in body composition
were accounted for, the data showed that less fat-free mass was
lost by subjects with a history of successful weight-loss attempts
than by subjects without such a history. The subjects did not provide information on whether the successful weight-loss attempts
were the consequences of diet, physical activity, drugs, or a combination of these; hence, we cannot explore this further.
We anticipated that the fraction of fat-free mass lost during a
loss of body weight would be larger than the fraction gained with
weight gain. The present study provided no support for this when
age-related changes in body composition that are independent of
weight change were accounted for. Hence, the results of the present study, which measured body-composition changes over time
in a large and representative sample of adult Danes with a high
response rate does not seem to provide a biological explanation
for why long-term weight loss is often unsuccessful. Nor do the
results offer support for the theory that weight cycling results in
a low percentage of fat-free mass, which may be associated with
increased mortality (28).
Some limitations to the present study should be noted. First,
it may be argued that impedance measurements are not sufficiently precise to detect small changes in body composition.
However, several studies have documented the reliability and
validity of this method of measuring body composition (29). In
addition, the measured difference in fractions of fat-free mass
gained and lost were small. Therefore, it is not likely that we
overlooked small significant differences. Furthermore, several
studies have shown that impedance performs well in measuring
body composition at the group level in epidemiologic surveys
but not as well when measuring individuals in clinical settings (29).
TABLE 3
Relative mean loss of fat-free mass as a fraction of body weight in
subjects who lost > 3 kg between the examinations in 1987–1988 and
1993–1994 with or without a previous intentional weight loss of > 5 kg1
Self-reported successful weight-loss attempts
Yes2
No
Men
0.30 ± 0.16 [19]
0.35 ± 0.17 [137]
Women
0.21 ± 0.18 [40]
0.27 ± 0.20 [85]
1–
x ± SD; n in brackets. Adjustment was made for age-related changes
in body composition, independent of weight changes. There were no significant within-sex differences between groups.
2
Significant interaction of weight-loss attempt group and sex, P = 0.0096
(ANOVA).
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FIGURE 5. Mean (± SD) change () in fat-free mass (FFM) as a percentage of the change in body weight (BW), by weight change in the 5 y
before the 1987–1988 examination (± > 1 kg) in men (solid lines) and
women (dotted lines) who gained () or lost ( ) > 3 kg BW between the
1987–1988 and 1993–1994 examinations. Adjustment was made for agerelated changes in FFM. There were no significant within-sex differences between groups, but the differences between men and women were
significant (P < 0.0001, ANOVA).
845
846
HEITMANN AND GARBY
were found to be associated with a more unfavorable relative
change in fat-free mass in men than in women, suggesting that
the metabolic and health consequences of weight change may be
dependent on sex to some degree.
We thank statisticians Michael Gamborg and Stine Segel for assistance
with the statistical analyses.
REFERENCES
1. Mikkelsen KL, Heitmann BL, Keiding N, Sørensen TIA. Independent effects of stable and changing body weight on total mortality.
Epidemiology 1999;10:671–8.
2. Muls E, Kempen K, Vansant G, Saris W. Is weight cycling detrimental to health? A review of the literature in humans. Int J Obes
Relat Metab Disord 1995;19(suppl):S46–50.
3. The National Task Force on the Prevention and Treatment of Obesity. Weight cycling. JAMA 1994;272:1196–202.
4. Wing RR. Weight cycling in humans: a review of the literature. Ann
Behav Med 1992;14:113–9.
5. Heitmann BL, Garby L. Composition of body weight differences in
subjects with the same body height. Eur J Clin Nutr 1998;52:619–20.
6. Steen SN, Oppliger RA, Brownell KD. Metabolic effects of
repeated weight loss and regain in adolescent wrestlers. JAMA 1988;
260:47–50.
7. Wadden TA, Bartlett S, Letizia KA, Foster GD, Stunkard AJ, Conill A.
Relationship of dieting history to resting metabolic rate, body composition, eating behavior, and subsequent weight loss. Am J Clin
Nutr 1992;560(suppl):203S–8S.
8. Prentice AM, Jebb SA, Goldberg GR, et al. Effects of weight cycling
on body composition. Am J Clin Nutr 1992;56(suppl):209S–16S.
9. Forbes GB. Lean body mass-body fat interrelationships in humans.
Nutr Rev 1987;45:225–31.
10. Brozek J, Grande F, Anderson JT, Keys A. Densitometric analysis of
body composition: revision of some quantitative assumptions. Ann
N Y Acad Sci 1993:110:112–40.
11. Kirchoff M, Schroll M, Kirkby H, et al. Screening I. Danmonica.
Part of the MONICA Project (Multinational Monitoring of Trends
and Determinants in CVD). CVD Epidemiol Newslett 1983;34:32.
12. Hollnagel H. The health structure of 40-year-old men and women in
the Glostrup area, Denmark. General design, sampling results and
referrals for further medical care. Dan Med Bull 1980;27:121–30.
13. Heitmann BL. Body fat in the adult Danish population aged 35–65
years: an epidemiological study. Int J Obes 1991;15:535–45.
14. Osler M, Heitmann BL, Schroll M. Ten year trends in the dietary
habits of Danish men and women. Cohort and cross-sectional data.
Eur J Clin Nutr 1997;51:535–41.
15. World Health Organization. Measuring obesity. Classification and
description of anthropometric data. Report on a WHO consultation
on the epidemiology of obesity. Copenhagen: WHO Regional Office
for Europe, Nutrition Unit, 1988.
16. Heitmann BL. Prediction of body water and fat in adult Danes from
measurement of electrical impedance. A validation study. Int J Obes
1990;14:789–802.
17. Saltin B, Grimby G. Physiological analysis of middle-aged and old
former athletes: comparison with still active athletes of the same
ages. Circulation 1968;38:1104–15.
18. Forbes GB. Longitudinal changes in adult fat-free mass: influence
of body weight. Am J Clin Nutr 1999;70:1025–31.
19. Forbes GB. Human body composition: growth, aging, nutrition and
activity. New York: Springer-Verlag, 1987:1–350.
20. WHO. Obesity: preventing and managing the global epidemic.
Report of a WHO consultation. World Health Organ Tech Rep Ser
2000;894:1–253.
21. Forbes GB. Body fat composition influences the body composition response to nutrition and exercise. Ann N Y Acad Sci 2000;904:
359–65.
Downloaded from ajcn.nutrition.org at PENNSYLVANIA STATE UNIV PATERNO LIBRARY on March 5, 2016
Furthermore, the particular equation used for computing fat and
fat-free mass in the present study was developed specifically for
the present population sample (16). When we reexamined the
data, we found the fractions of weight change made up by fatfree mass to be independent of the size of the weight change
(data not shown). Hence, measurement error did not seem to be
a problem in the present study.
Second, we cannot exclude the possibility that the measurement of leisure-time physical activity may have been subject to
misclassification and was too crude to differentiate between
sedentary and more active individuals. However, the questionnaire was found to have high validity when compared with fitness and other measures of activity (17), has been used for
> 30 y in Scandinavia, and was shown to be a strong predictor of
risk factors for all causes of death and total mortality (30, 31).
Although we cannot exclude the possibility that the crude measure of physical activity was partly responsible for the lack of difference in results between the active and inactive subjects, the
present data do not provide evidence that differences in physical
activity are responsible for the sex difference.
A third limitation of the present study may be the lack of
information about the time course of the weight changes. Rapid
weight changes may involve a relatively larger change in fat-free
mass than do gradual weight changes (25); these 2 types of
weight changes were not analyzed separately in the present
study. Hence, any possible metabolic differences between
adapted and transitional changes cannot be ascertained. Indeed,
whether men experience more rapid weight changes than do
women is unknown, but the possibility cannot be excluded that
the sex differences may relate to this. On the other hand, during
the 6 y between the examinations in 1987–1988 and 1993–1994,
the women generally reported more weight-loss attempts that
resulted in a weight loss of > 5 kg than did the men, suggesting
that the women may have experienced more periods of rapid
weight loss than did the men.
Finally, the reliability of self-reported information on intentionality of weight loss may be limited, as pointed out by French
et al (32). Furthermore, it is likely that in a population sample
such as that in the present study, subjects tend to cycle in weight
above and below an average level with an unknown periodicity,
which may not be equivalent to the 6-y weight changes reported
here. Hence, the measurement time points may be considered
“snapshots,” catching some on their way up in weight and others
on their way down. Indeed, surveys done at different times are
likely to catch different people in weight-gaining and -losing
groups, as indicated by the fact that twice as many subjects who
reported weight gains in the 5 y before the study fell into the
weight-loss group than into the weight-gain group at subsequent
examinations. In other words, regression toward the mean may
be part of the observed result. However, the fact that weight
changes in the previous 5 y did not influence the composition of
the subsequent weight changes does not support the importance
of regression toward the mean.
The present study, in which there was a high response rate
from a large and representative sample of the Danish population,
showed no significant within-sex difference in the fraction of
weight lost or gained as fat-free mass. The hypothesis that
weight cycling may result in adverse health effects by causing a
relative loss of fat-free mass cannot be supported by these data.
On the other hand, even after taking into account percentage
body fat and age-related changes in fat-free mass, weight changes
COMPOSITION OF WEIGHT CHANGE
28. Heitmann BL, Eriksson H, Ellsinger BM, Mikkelsen KL, Larsson B.
Mortality associated with body fat and body mass index among
60-year-old Swedish men—a 22 year follow-up. The study of men
born in 1913. Int J Obes Relat Metab Disord 2000;24:33–7.
29. Heitmann BL. Impedance: a valid method in assessment of body
composition? Eur J Clin Nutr 1994;48:228–40.
30. Lissner L, Bengtsson C, Björkelund C, Wedel H. Physical activity
levels and changes in relation to longevity: a prospective study of
Swedish women. Am J Epidemiol 1996;143:54–62.
31. Andersen LB, Schnohr P, Schroll M, Hein H. All-cause mortality
associated with physical activity during leisure time, work, sports,
and cycling to work. Arch Intern Med 2000;160:1621–8.
32. French SA, Jeffery RW, Folsom AR, Williamson DF, Byers T.
Weight variability in a population-based sample of older women:
reliability and intercorrelation of measures. Int J Obes Relat Metab
Disord 1995;19:22–9.
Downloaded from ajcn.nutrition.org at PENNSYLVANIA STATE UNIV PATERNO LIBRARY on March 5, 2016
22. Janssen I, Ross R. Effects of sex on the change in visceral, subcutaneous adipose tissue and skeletal muscle in response to weight loss.
Int J Obes Relat Metab Disord 1999;10:1035–46.
23. Ballor DL, Poehlman ET. Exercise-training enhances fat-free mass
preservation during diet-induced weight loss: a meta-analytical
finding. Int J Obes Relat Metab Disord 1994;18:35–40.
24. Leibel RL, Rosenbaum M, Hirsch J. Changes in energy expenditure resulting from altered body weight. N Engl J Med 1995;332:
621–8.
25. Garrow JS, Summerbell CD. Meta-analysis: effect of exercise, with
or without dieting, on the body composition of overweight subjects.
Eur J Clin Nutr 1995;49:1–10.
26. Waaler HT. Hazard of obesity—the Norwegian experience. Acta
Med Scand Suppl 1988;723:17–21.
27. Forbes GB. Do obese individuals gain weight more easily than
nonobese individuals? Am J Clin Nutr 1990;52:224–7.
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