Novo weight-loss drug may preserve lean body mass better than Lilly’s, study finds

HealthInternationalNovo weight-loss drug may preserve lean body mass better than Lilly's, study findsBy Reuters -Apr 17, 2026Eli Lilly’s  GLP-1 ​drug tirzepatide yields greater weight loss on average than Novo Nordisk’s  semaglutide, but at a greater expense ‌to muscles and connective tissues, according to a study published this week ahead of peer review. Tirzepatide, sold as Zepbound and Mounjaro, and semaglutide, under the brand names Wegovy and Ozempic, have become wildly popular for weight loss and have demonstrated other health benefits, such as heart-protective properties. But ​there has been concern that they induce loss of muscle and other components of lean body mass along with ​fat. The researchers analyzed data on roughly 1,800 patients using tirzepatide and 6,200 using semaglutide. Tirzepatide was consistently ⁠associated with greater loss of lean body mass than semaglutide. Tirzepatide patients lost an average of 1.1% more lean body ​mass after three months and 2% after 12 months of continuous use, the analysis by Massachusetts-based data analytics firm nference found. “This ​suggests that patients shouldn’t simplistically be thinking, ‘I want to lose X amount of weight and I’ll go with the option that delivers greater weight loss,’” said study leader Venky Soundararajan of nference on the study data published online. Patients were tracked before and during treatment either with low radiation ​scans or with “smart” scales that estimate body fat percentage, muscle mass, bone mass, and other components. The study cannot explain why lean ​body mass loss was greater with tirzepatide, which mimics the hormones GLP-1 and GIP, compared with semaglutide, which only mimics GLP-1. Mimicking the ‌hormones ⁠slows digestion and makes patients feel full. A Novo spokesperson did not comment on the current study but said changes in muscle mass did not significantly differ between semaglutide and placebo groups in clinical trials, and physical function was preserve...