Effects of Incretin-Based Therapies, Diet and Exercise Interventions, and Bariatric Surgery on Fat-Free Mass in Adults With Overweight or Obesity: A Systematic Review and Meta-Analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 42324178 · doi:10.1111/dom.71006
What was done
Authors conducted a systematic review and meta-analysis of randomized controlled trials published between 2015 and October 2025 across PubMed, Cochrane Library, and Embase. Eligible studies included adults with overweight or obesity (with or without type 2 diabetes) achieving ≥10% total weight loss via diet and exercise, incretin-based therapies, or bariatric surgery. The trials measured fat-free mass (FFM) or muscle mass using DEXA, CT, or MRI. A total of 21 studies (12 diet and exercise, 5 incretin-based, 4 bariatric surgery) comprising 1,334 participants were analyzed.
What was found
Pooled absolute reductions in FFM were: - Diet and exercise interventions: -1.8 kg (95% CI: -2.6, -1.0) - Incretin-based therapies versus placebo: -4.8 kg (95% CI: -5.6, -3.9) - Bariatric surgery: -9.1 kg (95% CI: -12.3, -6.0) The proportion of total weight loss attributable to FFM was: - Diet with/without exercise: 14.9% (22.3% for diet without exercise; 7.7% for diet with exercise) - Incretin-based therapies: 33.3% - Surgical interventions: 34.2%
Why it matters
Weight loss from incretin therapies and bariatric surgery leads to substantial lean tissue loss (roughly one-third of total weight lost), whereas combining dietary intervention with exercise significantly preserves fat-free mass.
Limits
The number of included trials for incretin therapies (n=5) and bariatric surgery (n=4) was small. The abstract did not differentiate between fluid loss and skeletal muscle mass within FFM, pooled different measurement modalities (DEXA, CT, MRI), and did not assess functional muscle strength or long-term clinical outcomes.
Cited by
- partial During aggressive caloric restriction or bariatric surgery without resistance training or high protein intake, approximately 40% of the weight lost is muscle.