Diet or exercise interventions vs combined behavioral weight management programs: a systematic review and meta-analysis of direct comparisons.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 25257365 · doi:10.1016/j.jand.2014.07.005
What was done
The authors conducted a systematic review and random-effects meta-analysis of randomized controlled trials directly comparing combined behavioral weight management programs (diet plus physical activity) with single-component programs (diet-only or physical activity-only). Inclusion criteria required adult participants with overweight or obesity (body mass index 25 or greater) and at least 12 months of follow-up. Nine databases were searched, and two reviewers extracted data independently. Weight change differences were evaluated at 3 to 6 months and 12 to 18 months using a baseline observation carried forward approach.
What was found
Eight studies with 1,022 total participants (majority women) were included. For combined programs versus diet-only (6 studies), there was no significant difference in weight loss at 3 to 6 months (-0.62 kg; 95% CI -1.67 to 0.44), but combined programs showed significantly greater weight loss at 12 months (-1.72 kg; 95% CI -2.80 to -0.64). For combined programs versus physical activity-only (5 studies), combined programs produced significantly greater weight loss at 3 to 6 months (-5.33 kg; 95% CI -7.61 to -3.04) and at 12 to 18 months (-6.29 kg; 95% CI -7.33 to -5.25).
Why it matters
This review shows that while diet alone matches combined interventions in the short term, combining diet and physical activity is necessary for superior long-term weight reduction. It also confirms that physical activity alone is substantially less effective for weight loss than combined programs.
Limits
The total evidence base was relatively small (8 trials, 1,022 participants) and participants were mostly female, limiting generalizability to males. The analysis relied on baseline observation carried forward for missing data. The abstract provides no data on intervention adherence, program intensity, or specific diet and exercise types.
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