Early changes in body composition with tirzepatide in adults with obesity: a real-world BIA study.

BACKGROUND: Tirzepatide induces substantial weight loss, but real-world data on early body composition changes remain limited. METHODS: We evaluated short-term changes in body composition in 51 adults with obesity treated with tirzepatide for 12 weeks, using bioelectrical impedance analysis. RESULTS: Body weight decreased by 8.75 kg (-8.18%, P < 0.001), primarily driven by fat mass reduction (-6.87 kg, P < 0.001), with a smaller decrease in soft lean mass (-1.73 kg, P < 0.001). Despite this, the relative proportion of lean mass increased (+3.00 percentage points, P < 0.001), indicating preferential fat loss. Approximately 78% of total weight loss was attributable to fat mass. CONCLUSION: These findings suggest that short-term tirzepatide therapy leads to favorable body composition changes, characterized by predominant fat loss and relative preservation of lean mass, supporting its metabolic benefit in real-world clinical practice.