Long-term weight loss after diet and exercise: a systematic review.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 15925949 · doi:10.1038/sj.ijo.0803015
What was done
A systematic review and meta-analysis searched Medline, Cochrane Library, and Lilacs databases through March 2003 without language restrictions. It included randomized controlled trials comparing diet plus exercise against diet alone in overweight and obese adults (BMI > 25, age ≥ 18) with at least 1 year of post-intervention follow-up. Two reviewers independently extracted data and assessed study quality using criteria adapted from the Jadad Scale and Delphi list.
What was found
From 33 identified trials, 6 studies directly comparing diet and exercise to diet alone were analyzed (active interventions lasted 10 to 52 weeks). Diet combined with exercise led to 20% greater initial weight loss than diet alone (13 kg vs 9.9 kg; z = 1.86, p = 0.063). At 1-year follow-up, the combined group maintained 20% greater weight loss (6.7 kg vs 4.5 kg; z = 1.89, p = 0.058). In both groups, nearly half of the initial weight loss was regained at 1 year.
Why it matters
It demonstrates that adding exercise to dietary interventions yields a modest long-term advantage for weight reduction, while highlighting that weight regain remains a substantial challenge across regimens.
Limits
Only 6 randomized trials met the strict inclusion criteria, and total participant numbers were not stated in the abstract. Observed differences between groups narrowly missed conventional statistical significance (p = 0.063 and p = 0.058). Specific exercise types, dietary protocols, and adherence rates were not reported.