Long-term weight loss after diet and exercise: A systematic review

Abstract

To assess the effectiveness of dietary interventions and exercise in long-term weight loss in overweight and obese people.
A systematic review with meta-analysis.
Overweight and obese adults-18 years old or older with body mass index (calculated as weight divided by the square of height in meters)>25.
Medline, Cochrane Library and Lilacs databases up to March 2003. Also, published reviews and all relevant studies and their reference lists were reviewed in search for other pertinent publications. No language restrictions were imposed.
Randomised clinical trials comparing diet and exercise interventions vs diet alone. All trials included a follow-up of 1 y after intervention.
Two reviewers independently abstracted data and evaluated the studies' quality with criteria adapted from the Jadad Scale and the Delphi list.
The estimate of the intervention's effect size was based on the differences between the comparison groups, and then the overall effect was calculated. A chi-squared test was used to assess statistical heterogeneity.
A total of 33 trials evaluating diet, exercise or diet and exercise were found. Only 6 studies directly comparing diet and exercise vs diet alone were included (3 additional studies reporting repeated observations were excluded). The active intervention period ranged between 10 and 52 weeks across studies. Diet associated with exercise produced a 20% greater initial weight loss. (13 kg vs 9.9 kg; z=1.86-p=0.063, 95%CI). The combined intervention also resulted in a 20% greater sustained weight loss after 1 y (6.7 kg vs 4.5 kg; z=1.89-p=0.058, 95%CI) than diet alone. In both groups, almost half of the initial weight loss was regained after 1 y.
Diet associated with exercise results in significant and clinically meaningful initial weight loss. This is partially sustained after 1 y.

Full text

REVIEW
Long-term weight loss after diet and exercise:
a systematic review
CC Curioni
1
* and PM Lourenc- o
1
1
Instituto de Medicina Social, Universidade do Estado do Rio de Janeiro. Rio de Janeiro, Brazil
OBJECTIVE: To assess the effectiveness of dietary interventions and exercise in long-term weight loss in overweight and obese
people.
DESIGN: A systematic review with meta-analysis.
SUBJECTS: Overweight and obese adultsF18 years old or older with body mass index (calculated as weight divided by the
square of height in meters)425.
DATA SOURCE: Medline, Cochrane Library and Lilacs databases up to March 2003. Also, published reviews and all relevant
studies and their reference lists were reviewed in search for other pertinent publications. No language restrictions were imposed.
STUDY SELECTION: Randomised clinical trials comparing diet and exercise interventions vs diet alone. All trials included a
follow-up of 1 y after intervention.
DATA EXTRACTION: Two reviewers independently abstracted data and evaluated the studies’ quality with criteria adapted from
the Jadad Scale and the Delphi list.
DATA SYNTHESIS: The estimate of the intervention’s effect size was based on the differences between the comparison groups,
and then the overall effect was calculated. A chi-squared test was used to assess statistical heterogeneity.
RESULTS: A total of 33 trials evaluating diet, exercise or diet and exercise were found. Only 6 studies directly comparing diet and
exercise vs diet alone were included (3 additional studies reporting repeated observations were excluded). The active
intervention period ranged between 10 and 52 weeks across studies. Diet associated with exercise produced a 20% greater
initial weight loss. (13 kg vs 9.9 kg; z ¼ 1.86Fp ¼ 0.063, 95%CI). The combined intervention also resulted in a 20% greater
sustained weight loss after 1 y (6.7 kg vs 4.5 kg; z ¼ 1.89Fp ¼ 0.058, 95%CI) than diet alone. In both groups, almost half of the
initial weight loss was regained after 1 y.
CONCLUSION: Diet associated with exercise results in significant and clinically meaningful initial weight loss. This is partially
sustained after 1 y.
International Journal of Obesity (2005) 29, 1168–1174. doi:10.1038/sj.ijo.0803015; published online 31 May 2005
Keywords: diet; exercise; systematic review; meta-analysis
Introduction
Obesity is a chronic disease that has reached epidemic
proportions in both developed and developing countries.
1
In
Brazil, prevalence of overweight and obesity increased more
than 50% in 30 y. About 40% of adults present some
degree of weight excess, and 10% are obese. However, the
best strategies to control the epidemic have not been settled
yet.
Obesity should be recognised as a disease and treated
accordingly, because it increases the risk of several diseases.
2
Weight loss (5–15% of the body weight) in obese individuals
reduces the risk factors associated with obesity.
2
Among the several strategies for obesity treatment, diet
and exercise are considered useful for losing weight in
moderately obese adults. However, it seems that even losing
weight with these approaches, most obese individuals do not
maintain the loss for long periods.
3–6
Unfortunately, there
are no accepted rules to guide interventions promoting
behaviour and lifestyle changes for an effective and perma-
nent weight loss.
The aim of the present study was to carry out a systematic
review with meta-analysis of randomised clinical trials
assessing the effectiveness of exercise combined with dietary
interventions in initial weight loss and its long-term
maintenance among overweight and obese people.
Received 22 September 2004; revised 13 April 2005; accepted 27 April
2005; published online 31 May 2005
*Correspondence: CC Curioni, Instituto de Medicina Social, Universidade
do Estado do Rio de Janeiro, Rua Sa
˜
o Francisco Xavier, 524, pavilha
˜
oJoa
˜
o
Lyra Filho, 71 andar, blocos D e E, Maracana
˜
Rio de Janeiro-RJ-CEP. 20559-
900, Brasil.
E-mail: c_curioni@uol.com.br
International Journal of Obesity (2005) 29, 1168–1174
&
2005 Nature Publishing Group All rights reserved 0307-0565/05
$
30.00
www.nature.com/ijo

Methods
Randomised controlled clinical trials of diet, exercise or both
in overweight or obese adult (lowest acceptable age 18 y)
patientsFbody mass index (weight divided by the square
of height in meters) 425 as defined by the World Health
Organization
1
Fwere considered for inclusion. The follow-
ing sources were included in the literature search process:
The Cochrane Controlled Trials Register (Cochrane Library),
Medline (US National Library of Medicine), and Lilacs (Latin
American and Caribbean Literature in Health Sciences), up
to March 2003. The search strategy used the following
keywords and variations: obesity, overweight, diet, exercise,
randomised clinical trial. Also, published reviews and all
relevant studies and their reference lists were reviewed in
search for other pertinent publications. No language restric-
tions were imposed. Studies were included if they had a
follow-up period after intervention of at least 1 y.
We compared data obtained immediately after interven-
tion period and after 1 y of unsupervised follow-up. Data
obtained after periods greater than 1 y were only considered
if the 1 y results were not described. Sensitivity analysis was
performed to explore differences resulting from the exclu-
sion of such studies.
Diet included any type of caloric restriction, and exercise
included any type of exercise in which it was possible to
quantify the recommended activity. Studies including
pregnant woman or children or the use of any medication
were excluded. Diet and exercise interventions could be
associated with behavioural therapy. However, studies of
behavioural therapy as the only intervention were excluded.
No restriction about health status was made. No pre-
specified weight loss after intervention was required.
Both authors independently considered studies for inclu-
sion. Initially, the reviewers scanned the titles, abstracts and
keywords of every article retrieved to determine whether it
met the predetermined eligibility criteria. In the presence of
any doubt about article inclusion, a final consensus decision
was taken after the full text was jointly reviewed.
The study quality was rated using specific quality criteria
adapted from the Jadad Scale and the Delphi list.
7,8
Sensitivity analyses were planned to evaluate the possible
influence of studies with methodological flaws such as high
dropout rates. Of all, 33 trials evaluating diet, exercise or diet
and exercise were found. A table with the excluded studies is
presented at the end of the article (Appendix A ).
For meta-analysis, three values were obtained in each
group: the sample size, the mean and its standard deviation.
The individual effect size of the intervention was obtained
from the magnitude of the differences between groups
(reduced weight in the combined intervention group in
relation to diet alone controls). The global effect was then
calculated with the respective 95% confidence intervals
through the inverse variance method. Initially a fixed effects
model was used presuming homogeneity among studies.
Heterogeneity between trial results was tested using a
standard chi-squared test with a significance level of
alpha ¼ 0.1 in view of the low power of such test. Data were
analysed using the statistical software Stata 6.0.
9
Weight loss percentage (and variance) immediately after
intervention and after 1 y was obtained through w. Where w:
(w1) early weight loss after intervention ¼ weight loss
immediately after intervention (post-intervention)/ baseline
weight,
(w2) weight loss after 1 y ¼ weight loss after 1 y follow-up/
baseline weight,
(w3) weight maintenance ¼ weight loss after 1 y follow-up/
early weight loss after intervention.
The standard deviation (SD) was calculated through the
formulae
10
:
S
2
¼ N  (a/b)  (1[a/b]); and SD ¼ Os
2
, where S
2
F
variance.
Results
Descriptive data of the included studies are presented in
Table 1. The sample size of the studies varied from 40 to 127
individuals with age ranging from 21 to 65 y. Three studies
were performed only with women, one only with men, and
two with patients of both genders. The length of the
intervention varied from 10 to 52 weeks, and follow-up
Table 1 Descriptive data of studies included in this paper
Reference Country n Sex Age Intervention Dropout rate (%) Length of treatment (weeks) Follow-up (months)
1. Borg et al
11a
Finland 90 M 35–50 D  D+E 24 32 24
2. Fogelholm et al
12
Finland 82 F 30–45 D  D+E 9.4 40 24
3. Wadden et al
13,b
USA 120 F 30–50 D  D+E 17 48 12
4. Fogelholm et al
14
Finland 82 F 30–45 D  D+E 9.4 40 24
5. Andersen et al
15
USA 40 F 21–60 D  D+E 17.5 16 12
6. Weinstock et al
16,b
USA 120 F 30–50 D  D+E 17 48 12
7. Wadden et al
17,b
USA 120 F 30–50 D  D+E 17 48 12
8. Skender et al
18
USA 127 F & M 25–45 D  E  D+E 19 52 12
9. Wing et al
19
USA 55 F & M 30–65 D  D+E 14.5 10 12
Abbreviations: USA, United States of America; F, female; M, male; D, diet; E, exercise; D+E, diet and exercise; studies excluded from analysis due to data duplicity are
in boldface.
a
Two groups with variable intensities of exercise in the original paper were grouped in a single group (using t-test) and compared to the diet only group.
b
Three groups with variable intensities of exercise in the original paper were grouped in a single group (using t-test) and compared to the diet only group.
Long-term weight loss after diet and exercise
CC Curioni and PM Lourenc- o
1169
International Journal of Obesity

from 12 to 24 months. In all but one study, patients were
seen once a week during the entire period of intervention,
usually in small groups. Among the included studies, some
presented duplicated data (12 and 14; 13, 16 and 17). For
data analysis, only the last published trials were included.
Therefore, six trials were analysed. With regard to the follow-
up, the end point chosen for the present analysis was 1 y
after the end of the intervention.
The baseline weight average varied from 83.5 to 106 kg
(Table 2). The dropout rate was less than 20% in all studies
except that from Borg et alF24% dropout rate.
11
This same
study only presented results at the end of a 23 months
follow-up (no data in 1 y after intervention). Therefore, a
sensitivity analysis was performed excluding this study.
Most studies only mentioned that that they constituted
a randomised controlled trial, only two actually describing
the randomising process.
11,12
No study gave information
about the blinding process nor made an intention-to-treat
analysis.
Individuals in the diet and exercise group had a mean
weight loss after intervention approximately 20% greater
than individuals in the diet group: 13.0710.4 kg vs
9.979.6 kg, p ¼ 0.063. Heterogeneity was not detected
through the chi-square test (Figure 1). The results are not
significantly changed if the study N.1
11
is excluded from the
analysis (22% greater mean weight loss in the diet and
exercise group: 12.9710.2 vs 9.477.7, p ¼ 0.066, 0.46–
0.01; 95%CI).
Table 2 Comparison of diet and exercise vs diet
Diet and exercise Diet
Study
(reference) N
Baseline weight
(kg)
Initial weight loss
(kg)
Weight loss after 1 y
(kg) N
Baseline weight
(kg)
Weight loss
intervention (kg)
Weight loss after 1 y
(kg)
Study 1
[11]
53 106.079.9 13.7713.6 5.1715.6
a
29 106.079.9 12.1714.9 5.3720.4
a
Study 2
[12]
53 91.372.0 13.8711.0 5.6714.0 29 93.271.6 11.2710.3 3.579.7
Study 3
[13]
91 96.0713.9 15.479.1 9.179.6 21 96.378.8 14.476.2 6.976.3
Study 5
[15]
20 83.678.6 8.373.8 6.776.7 20 90.5713.5 7.974.2 7.876.2
Study 8
[18]
21 100.1727.4 8.9711.5 2.276.7 15 98.5725.9 6.877.8 +0.977.7
Study 9
[19]
27 105.375.8 8.976.2 7.976.9 28 100.174.9 6.475.2 3.975.2
Total 265 97.4716.1 13.0710.4 6.778.3 142 97.8 710.7 9.979.6 4.5711.3
a
The follow-up period was 23 months (unsupervised).
ll
ll l
l
Figure 1 Meta analysis of weight-loss after intervention comparing diet and exercise vs diet.
Long-term weight loss after diet and exercise
CC Curioni and PM Lourenc- o
1170
International Journal of Obesity

As to weight loss maintenance after 1 y, diet and exercise
also resulted in 20% greater weight loss than diet alone:
6.778.3 vs 4.5711.3 kg, p ¼ 0.058 (Figure 2). The exclu-
sion of the previously mentioned study
11
resulted in slightly
different findings of the meta-analysis, however, with more
marked differences favouring the diet and exercise group
(26% greater weight reduction with diet and exercise
group: 7.1710.3 vs 4.477.7, p ¼ 0.03, 0.50 to 0.03;
95% CI).
The percentages of weight loss from baseline weight were:
w1 (immediately after intervention)F1375.5% for the diet
and exercise group and 1073.6% for the diet group; w2
(after 1 y)F6.874.1 and 4.672.5%, respectively. There was a
similar weight regain in both groups after 1 y: w3F5078.2
and 5075.9%. These results are not influenced if study N.1
11
is excluded (data not shown).
Discussion
The present study indicates that programs including both
diet and exercise produce greater weight loss than diet alone
in obese and overweight individuals soon after the interven-
tion period and after 1 y of follow-up. In both groups, the
magnitude of weight reduction immediately after interven-
tion as after 1 y of follow-up is compatible with clinically
significant benefitsFreduction of cardiovascular risk factors;
improvement of glicemic control and hyperinsulinemia in
diabetics; decrease of blood pressure, total cholesterol, LDL-
cholesterol and triglyceride levels; increase of HDL-choles-
terol concentrations.
2,20
Weight regain in individuals in both interventions
approached 50%. Adding exercise to diet did not produce a
better long-term maintenance of the lost weight. Fogelholm
and Kukkonen-Harjula
21
published a review of physical
activity to prevent weight gain analysing both observational
studies and randomised clinical trials. Results from observa-
tional studies (but not those from the clinical trials also
analysed) suggested that exercise leads to successful weight
loss maintenance.
21
Also, in contrast to some studies,
22–27
we
observed that an initial greater weight loss was very hard to
sustain. Our results suggest that individuals changed their
lifestyle, but just for a short period, since they partially
returned to their previous patterns. This study only evalu-
ated weight loss, which did not allow us to determine the
reasons for weight regain. Additional outcomes would be
necessary to evaluate possible associationsFbehavioural and
physiologic factors, among others. It would be also impor-
tant to explore differences among individuals that regained
weight and those who maintained the lost weight.
The great difficulty and limitation of weight loss studies
is that they only report the mean group weight changes and
not the frequency of expected responses to the interven-
tions, ie, how many people actually lost weight. Means are
not appropriate to evaluate how many people attained a
clinically significant weight loss.
A number of systematic reviews on weight loss and
maintenance related to diet and physical activity have been
published. McTigue et al
28
reported that counselling on diet
or physical exercise and behavioural interventions resulted
in small to moderate degrees of sustained weight loss (3–5 kg)
Figure 2 Meta analysis of weight-loss maintenance after 1 y of follow-up comparing diet and exercise vs diet.
Long-term weight loss after diet and exercise
CC Curioni and PM Lourenc- o
1171
International Journal of Obesity

over at least 1 y. However, the results of the studies could not
be grouped, and those reporting some success in weight
maintenance were commented on individually. Miller et al
29
reported an initial weight loss of 11% of the baseline weight,
and of 7–9% after 1 y of follow-up. Anderson et al
6
reported
maintenance of 11% reduction in initial weight after 1 y of
follow-up. All these systematic reviews included only cohort
studies. The present study, on the other hand, included only
controlled clinical trials, which evaluate more accurately the
true intervention effect on the long-term weight loss.
30
Other systematic reviews on obesity management are
worth mentioning. In general, their results support our
own findings. In the review from Fogelholm and Kukkonen-
Harjula,
21
most clinical trials did not find that exercise
training improve weight maintenance. Glennny et al
31
in
another review evaluating many aspects of obesity treatment
and prevention, reported that most trials included demon-
strate weight regain either during or after the intervention
period.
A number of limitations of the present analysis should
be acknowledged. Most studies were of poor quality: few
described clearly the randomising process and none included
intention-to-treat analyses. In addition, subgroup analyses
by sex, age and initial weight would be important to explore
effect size differences. The funnel plot to investigate the
existence of publication bias could not be evaluated. With a
limited number of studies included, this analysis has limited
power to detect bias and the results can be distorted.
32
In conclusion, the present study confirms the important
role of diet and exercise in short and long-term weight loss.
Diet associated with exercise can provide greater initial
weight-loss than diet alone. Most importantly, we have
shown that after 1 y the combined approach is also
associated with greater weight loss than diet alone, in a
range compatible with clinically relevant benefits. Both
types of studied interventions are, however, associated with
partial long-term weight regain (50% in 1 y). Programs to
treat obese and overweight individuals should explore the
best strategies to promote prolonged changes in lifestyle
leading to caloric adequacy and increase in physical activity.
Future researchers should identify program patterns that
are more effective in the long-term. Although dropouts
cannot always be controlled, all effort should be made to
verify their reasons. This would allow a better knowledge of
the factors that affect adherence to therapeutic programs.
The results should also include outcomes such as frequency
of pre-established responses to interventions. In order to
attain higher levels of scientific evidence, future randomised
clinical trials should also describe the randomisation and
blinding processes and include intention-to-treat analyses.
Acknowledgements
The authors thank: Rosely Sichieri, MD, PhD, Instituto de
Medicina SocialFUniversidade do Estado do Rio de Janeiro;
and Charles Andre
´
, MD, PhD, Universidade Federal do Rio de
Janeiro for valuable suggestions.
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Appendix A
Table A1 Table of excluded trials
Study reference
Baseline BMI (kg/m
2
)or
% of ideal weight Age(Y) Intervention
Duration of
intervention
(Weeks)
Follow-up
(Months) Reason for exclusion
King et al
33
120–160% 30–59 D  E  C 52 12 There is no diet+exercise group
Jeffery et al
34
14–32 kg over ideal
weight
25–45 D+E  C 52 18 There is no diet only group
Pavlou et al
35
122% 26–52 D  D+E 8 18 Information only available in graph, with
values not described
Perri et al
36
160% 22–60 BT+E+M  BT+E  BT+
M  BT
20 18 There is no diet intervention, only behavioral
therapy (BT) in groups; the M group was
periodically contacted during follow-up.
Sikand et al
37
170–200% 21–60 D  D+E 20 24 The follow-up weight is self-reported; poor
methodological quality
Tuomilehto et al
38
26.5–35.9 40–65 D+E  C 52 12 There is no diet only group
Uusitupa et al
39
26.5–35.9 40–65 D+E  C 52 12 There is no diet only group
van Dale et al
40
32.3 (mean) 34 (mean) D  D+E 12–14 18–42 Not a randomized clinical trial: subjects
entered in three different diet-exercise studies
BT, behavioral therapy; C, control; D, diet; E, exercise; M, multicomponent maintenance program. Other studies exclusively comparing two different interventions
of diet were also excluded.
41–57
Long-term weight loss after diet and exercise
CC Curioni and PM Lourenc- o
1174
International Journal of Obesity