Scientists Test Drugs to Cut GLP-1 Muscle Loss as 25% to 40% of Weight Shed Is Lean Mass
Updated
Updated · Scientific American · May 19
Scientists Test Drugs to Cut GLP-1 Muscle Loss as 25% to 40% of Weight Shed Is Lean Mass
7 articles · Updated · Scientific American · May 19
Eli Lilly’s phase 2 trial paired bimagrumab with semaglutide and delivered 22% weight loss over 72 weeks, with 92% of pounds lost coming from fat versus 76% on semaglutide alone.
That push reflects a growing concern that GLP-1 drugs such as Wegovy, Ozempic and Zepbound can strip muscle alongside fat; studies estimate users may lose muscle mass equivalent to 20 years of age-related decline within a few years.
Older adults are a key focus because muscle naturally falls about 30% between the 20s and 80s, and added loss can raise risks of falls, fractures, weaker mobility and metabolic decline.
Researchers are also testing SARMs, but safety remains unclear, and bimagrumab’s earlier studies increased muscle without clear gains in walking speed or endurance.
Until larger human trials prove these add-on drugs safe and effective, experts still point to resistance training and roughly 1.2 to 1.6 grams of protein per kilogram a day as the best-supported protection.
Beyond Ozempic: Will new drugs let you lose only fat and even gain muscle?
New studies say Ozempic's muscle loss is modest. Is the panic overblown?
Maximizing Fat Loss, Preserving Muscle: BELIEVE Trial’s 22% Weight Loss Breakthrough With Bimagrumab and Semaglutide
Overview
The BELIEVE trial marks a major breakthrough in obesity treatment by combining bimagrumab and semaglutide. Published in 2026, this phase 2 study showed that participants lost an average of 22.1% of their body weight over 72 weeks. Impressively, 92% of this weight loss came from fat, while lean muscle loss was minimized to just 2.9%. This significant preservation of muscle mass sets the combination therapy apart from existing treatments, which often lead to unwanted muscle loss. The BELIEVE trial’s results highlight a new direction in weight management, focusing on healthier, higher-quality weight loss.