This meta-analysis examined the effects of different weight loss interventions on symptoms of depression, and compared those effects across different types of treatment. In general, we found that nearly all non-pharmacologic weight loss approaches resulted in a significant reduction in symptoms of depression, again contradicting early reports that dieting and weight loss precipitated mood disturbance. Comparisons of treatment types found that lifestyle modification induced significantly greater reductions in symptoms of depression than control and non-dieting interventions. Reductions in symptoms of depression were marginally greater with lifestyle modification than with alternative weight loss interventions, including dietary counseling and exercise-alone. Exercise-alone also was superior to control for reducing symptoms of depression. The significant between-groups effect sizes were in the small to medium range (78
Two findings from the present analyses indicate that the reductions in symptoms of depression cannot be fully explained by weight loss. First, there were significant reductions in symptoms of depression with non-dieting programs, which were not intended to – and did not – induce weight loss. The beneficial effect of non-dieting on symptoms of depression may be due to the cognitive-behavioral strategies that encourage self-acceptance regardless of body weight. The same strategies may also reduce perceptions of stigma and of the severity of weight-related impairments, while fostering a sense of mastery and self-control that may have been previously limited in obese participants. Second, our meta-regression analysis of the lifestyle modification groups revealed that the within-groups effect for weight change was unrelated to the within-group effect for changes in symptoms of depression. That is, weight loss was not associated with increased or decreased symptoms of depression. Furthermore, neither the duration of treatment nor the intensity of the counseling intervention was related to the magnitude of change in depressive symptoms. Thus, other elements of treatment were likely responsible for the favorable effect on mood. Like those who received non-dieting interventions, obese individuals in lifestyle modification also may have achieved cognitive or behavioral changes that improved mood independently of the weight loss that resulted from those changes. They also may have benefited from the social support of their fellow group members and treatment providers. (Nearly all lifestyle modification programs studied here were delivered in group format.)
The meta-regression revealed that inclusion of a supervised exercise component was favorably related to changes in symptoms of depression among lifestyle modification participants. Several studies support a direct link between increased physical activity and improvements in mood (79
). An alternative explanation for the added benefit of supervised physical activity sessions (which are typically done in groups) is that they carried many of the same benefits of the group counseling sessions, described above. Clinically, many obese patients report embarrassment about exercising at health clubs because they assume they will be unfavorably compared with others whom they perceive to be more fit, more attractive, more coordinated, or generally more competent to exercise. Exercising in the company of fellow participants in weight loss programs may have helped to normalize participants’ perceptions of themselves in relation to others.
Our generally favorable findings contradict those of a previous meta-analysis that reported little improvement in quality of life (including depression) in randomized controlled weight loss trials (81
). Maciejewski et al. analyzed results from eight studies that measured symptoms of depression with the BDI and found that the random-effects comparison of treatment and control interventions yielded a nonsignificant pooled effect size of 0.07 (95% CI = −0.32 to 0.46) (81
). However, there are substantive differences between that analysis and ours, particularly with respect to the definitions of treatment and control arms. In only three of the eight studies included in the previous meta-analysis did the control participants receive no treatment (60
), and in one of those, the active treatment was acupuncture (83
). In three other studies, there were few differences between the interventions that were defined as treatment and control: group-based vs. individual lifestyle modification (84
); cognitive-behavioral counseling plus nutrition education vs. cognitive-behavioral counseling alone (85
); and lifestyle modification vs. dietary counseling (86
). In two other studies (which also were included in the present analysis), the comparisons appeared to be between lifestyle modification and non-dieting interventions. However, Maciejewski et al. classified the lifestyle modification program as the treatment in one study (38
) and as the control in the other (54
). By contrast, the present study provided operational definitions of treatment types and included separate analyses for each comparison that appeared frequently enough in our search results to support a meta-analysis.
Our findings directly contradict the notion that intentional weight loss interventions adversely affect psychological well-being. Keys’ report in 1950 on the induction of neurotic – and even psychotic – symptoms with calorie restriction (30
) remains of concern to some researchers and clinicians. We note, however, that the participants in Keys’ classic starvation study were normal weight volunteers whose energy intake was restricted by 50%, and whose weight was reduced 26% (rendering participants clinically anorectic). Thus, the adverse effects observed should not be generalized to overweight and obese persons who are prescribed more modest reductions in calorie intake and lose approximately 10% of initial weight. In 1957, Stunkard described “dieting depression” as a constellation of negative affective and psychomotor symptoms that was found in some obese persons who engaged in weight loss therapy (31
). Certainly, some people experience depression and other psychological distress while trying to lose weight. However, results of the Look AHEAD study, a large randomized controlled trial that is examining the effects of intentional weight loss in overweight and obese patients with type 2 diabetes, found that the incidence of significant symptoms of depression was significantly lower among those who received an intensive lifestyle intervention than among controls, who received usual care (29
). These findings, as well as those from the present meta-analysis should allay any remaining concerns that attempting to lose weight with diet, exercise, and behavior therapy may be harmful to the psychosocial status of obese patients without pre-existing psychopathology.
Concerns, however, remain about the psychiatric side effects of pharmacologic agents. Christensen et al. reported that patients treated with rimonabant were significantly more likely to discontinue treatment due to mood disorders (odds ratio = 2.5) and anxiety disorders (odds ratio = 3.0) than those who received placebo (33
). Our analysis, which found no difference in changes in symptoms of depression between pharmacologic interventions and placebo, must be interpreted cautiously for two reasons. First, our analyses only included mean changes on measures of depressive symptoms. The incidence of clinically significant distress and discontinuation rates were not included. Second, baseline and post-treatment depression scores were only reported for 79% to 82% of patients in the three studies of rimonabant that were included in the present meta-analysis. Thus, the analyzed data were incomplete. Separate examination of groups treated with sibutramine found significant improvements in symptoms of depression, suggesting that all pharmacologic weight loss interventions should not be assumed to have similar effects on mood.
Four additional limitations of the present meta-analysis must be noted. First, we were unable to include all relevant studies due to unavailability of necessary data. In particular, studies published before 2000 are underrepresented. Second, at least 9 of the included studies reported results of completers’ analyses, rather than the more conservative intent-to-treat analyses. The type of analysis was not specified in nearly half of the studies. Third, the applicability of the present findings to the obese treatment-seeking population, as a whole, is questionable. Trials of weight loss interventions routinely exclude persons with significant psychological distress at screening. Given the elevated rates of psychopathology in obese individuals (4
), the samples in the included studies must be considered highly selected. As a result, this analysis does not fully address the potential adverse effects of dieting and weight loss on mood in obese individuals who suffer from depression, binge eating disorder, or other psychiatric disorders, prior to undertaking weight reduction.
Collectively, our findings suggest that the effects of most weight loss interventions – particularly non-pharmacologic therapies – on mood are favorable when weight loss is undertaken by obese individuals who are generally free of depression and other psychopathology. While exercise-alone interventions had the largest within-treatment pooled effect size, lifestyle modification programs, which incorporated exercise with dietary instruction and behavior therapy, were found to induce marginally or significantly greater reductions in symptoms of depression than other non-pharmacologic treatments. Future research on the effects of intentional weight loss on mood would benefit from including persons with higher levels of baseline distress, using diagnostic measures (based on the latest edition of the Diagnostic and Statistical Manual of Mental Disorders) rather than symptom inventories to assess depression, and expanding outcomes to include incidence and resolution of clinically significant distress among participants in weight loss trials.