New research published in Nature Medicine suggests that combining the monoclonal antibody apitegromab with weight-loss medications like tirzepatide may significantly reduce the loss of lean body mass. While GLP-1 based drugs effectively treat obesity, clinical data indicates that 25–40% of total weight loss often comes from non-fat components, including vital muscle tissue.
How does apitegromab preserve muscle during weight loss?
Apitegromab functions by blocking myostatin, a protein that naturally inhibits muscle growth. In a trial of 102 participants, researchers found that those receiving apitegromab alongside tirzepatide experienced a more favorable body composition change than those on a placebo. According to the study, participants taking apitegromab lost an average of 1.6kg (3.5lb) of lean mass, while the placebo group lost an average of 3.5kg. This equates to a 55% greater retention of lean mass for the treatment group, according to the findings reported in Nature Medicine.
Lean body mass is metabolically active and burns more calories than fat tissue. Maintaining it is linked to a lower risk of type 2 diabetes and improved physical strength.
Why does muscle loss matter for patients on weight-loss jabs?
Prof. Alexander Miras, an obesity expert at Ulster University, notes that while GLP-1 drugs improve overall “functionality”—making daily tasks easier—they simultaneously carry the risk of reducing muscle strength. “This means that [people] may be less able to lift heavy weights, for example, or walk up a hill,” Miras said. By mitigating the effects of these medications on muscle tissue, drugs like apitegromab could potentially enhance the physical benefits of weight-loss treatments.
What are the limitations of the current research?
The trial, funded by the drug’s producer, Scholar Rock, was relatively small and short in duration, lasting 24 weeks. Prof. Naveed Sattar, a cardiometabolic medicine expert at the University of Glasgow, emphasized that larger, longer-term trials are essential to confirm safety and health outcomes. “It’s too early to say whether this actually benefits peoples health or ability to move or function better,” Sattar explained. He also advocates for supporting patients in increasing physical activity, which remains a natural way to maintain muscle mass.
If you are currently prescribed weight-loss medication, focus on strength-based physical activity. Framing exercise as a sustainable, enjoyable habit rather than a medical requirement can improve long-term adherence and health.
Frequently Asked Questions
Why do weight-loss drugs cause muscle loss?
Rapid weight loss often results in the body breaking down both fat and non-fat components, including muscle. Research suggests 25–40% of weight lost on these medications may be lean body mass.
Is apitegromab currently available?
Apitegromab is an experimental treatment. The recent study published in Nature Medicine was an early-stage trial, and further research is required to determine its long-term safety and efficacy.
What is the main benefit of retaining lean mass?
Retaining lean mass helps maintain physical strength, supports metabolic health by burning more calories than fat, and may reduce the risk of developing type 2 diabetes.
Are you interested in the latest developments in metabolic health and weight management? Subscribe to our newsletter for evidence-based updates or join the conversation in the comments below to share your thoughts on the future of obesity treatment.
