The systematic review and meta-analysis titled ‘Body Composition Remodelling During GLP-1-Based Therapy’ investigates the effects of glucagon-like peptide-1 (GLP-1) receptor agonists on body composition, particularly focusing on adiposity, muscle quantity, and muscle quality. Conducted by Lopes Menezes et al., this study synthesizes findings from nineteen studies that met specific eligibility criteria.
Background
Body composition changes during GLP-1-based therapy remain incompletely characterized. This systematic review aims to clarify the effects of GLP-1 receptor agonists on body composition, particularly in adults. The authors utilized a predefined physiological framework to evaluate outcomes related to adiposity, muscle quantity, muscle quality, and overall body weight.
Methods
The authors conducted a comprehensive search through databases such as PubMed, Embase, and Cochrane CENTRAL, focusing on studies that reported longitudinal body composition outcomes in adults undergoing GLP-1 therapy. The primary analyses prioritized comparative evidence, ensuring that only one physiologically coherent outcome per study and domain was included in the meta-analysis.
Results
The analysis included nineteen studies, comprising both comparative and exploratory single-arm investigations. Notably, three comparative studies contributed to the primary adiposity meta-analysis, while two studies informed the muscle quantity analysis. The findings suggested a trend toward greater reductions in adiposity during GLP-1 therapy, although the evidence was characterized by substantial heterogeneity and wide confidence intervals. The muscle quantity outcomes were similarly heterogeneous and imprecise, preventing definitive conclusions.
Exploratory single-arm analyses indicated reductions in adiposity and body weight; however, changes in muscle quantity varied significantly across studies. The narrative evaluation of muscle quality outcomes was hindered by methodological inconsistencies and incomplete variance reporting.
Conclusions
The current comparative evidence indicates a potential direction toward greater reductions in adiposity with GLP-1-based therapy. However, the limited number of comparative studies, along with the substantial heterogeneity and low certainty of evidence, restricts the ability to draw definitive conclusions regarding fat loss or muscle preservation. Importantly, reductions in lean mass should not be equated with sarcopenia, although there is insufficient evidence to rule out clinically relevant muscle loss in vulnerable populations. The authors emphasize that these findings should be viewed as hypothesis-generating, necessitating further research with adequately powered studies that utilize standardized assessments of muscle metrics.
What this study does not show
This study does not establish definitive outcomes regarding the effectiveness of GLP-1 therapy on muscle preservation or fat loss due to the limited number of comparative studies and significant heterogeneity in the results.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Partial
- Clinical utility: Not established
The evidence is based on a systematic review and meta-analysis of human studies.