Semaglutide associated with 35.2% of weight loss as lean mass versus 26.2% with lifestyle interventions

This systematic review and meta-analysis examined the impact of incretin-based therapies on body composition in adults with overweight or obesity. The analysis included data from 15 782 participants. The intervention group received incretin-based therapies, which encompass GLP-1 receptor agonists and dual GLP-1/GIP agonists. The comparator group underwent intensive lifestyle interventions. The primary outcome measured was the absolute change in lean mass in kilograms and the proportion of total weight lost as lean mass. The study setting was not reported. Safety and tolerability data, including adverse events and discontinuations, were not reported in the source material. The follow-up duration was not reported.

The meta-analysis found that the proportion of total weight lost as lean mass with semaglutide was 35.2%. The 95% confidence interval for this estimate ranged from 31.5% to 38.9%. For tirzepatide, the proportion of total weight lost as lean mass was 25.4%, with a 95% confidence interval of 22.8% to 28.0%. Liraglutide was associated with a proportion of total weight lost as lean mass of 26.8%, with a 95% confidence interval of 23.1% to 30.5%. In the comparator group, intensive lifestyle interventions resulted in a proportion of total weight lost as lean mass of 26.2%. The 95% confidence interval for lifestyle interventions was 24.1% to 28.3%.

When comparing incretin agonists directly to lifestyle interventions, the analysis showed comparable proportional lean mass loss. The p-value for this comparison was 0.42. A separate analysis of lifestyle interventions combined with resistance training showed a proportion of total weight lost as lean mass of 17.5%. The 95% confidence interval for this combined approach was 14.2% to 20.8%. The source data did not provide absolute numbers for these outcomes.

Heterogeneity across the included studies was moderate, with an I-squared value of 68%. The certainty of evidence was evaluated using the GRADE framework. Funding sources and potential conflicts of interest were not reported. The study did not report specific adverse events, serious adverse events, or rates of discontinuation.

These findings suggest that while pharmacologic agents like semaglutide promote significant weight loss, a substantial portion of that loss may be lean mass. The data indicate that the proportion of weight lost as lean mass with semaglutide (35.2%) is numerically higher than with lifestyle interventions (26.2%), yet the comparison between incretin agonists and lifestyle interventions yielded a p-value of 0.42, suggesting comparable proportional lean mass loss in the aggregate analysis. However, the addition of resistance training to lifestyle interventions reduced the proportion of weight lost as lean mass to 17.5%.

Clinical implications highlight the importance of muscle preservation strategies. Muscle mass can be significantly preserved by integrating resistance training, adequate protein intake, and body composition monitoring into weight-loss treatment programs. This is particularly relevant given that the proportion of total weight lost as lean mass with lifestyle plus resistance training was 17.5%, which is lower than the proportions observed with pharmacologic monotherapy. The practice relevance emphasizes that treatment programs should not rely solely on weight reduction metrics without considering body composition.

Several questions remain unanswered. The specific mechanisms driving the differences in lean mass loss between agents are not detailed in the source. The long-term sustainability of these body composition changes was not reported. The impact of varying dosages or treatment durations on lean mass preservation was not reported. Furthermore, the lack of reported safety data limits the ability to fully assess the risk-benefit profile of these interventions regarding muscle loss. The moderate heterogeneity observed (I = 68%) suggests that study populations or protocols may vary significantly, which could influence the generalizability of the findings.