Protect muscle on GLP‑1s

Glucagon-like peptide-1 drugs help people eat less and lose weight, but some of that weight can come from lean mass, including muscle. (nejm.org) These medicines mimic gut hormones that slow stomach emptying and increase fullness. In a 2026 New England Journal of Medicine review, muscle and bone loss were listed among the concerns that come with sustained weight loss on these drugs. (nejm.org) In the STEP 1 trial, 1,961 adults with overweight or obesity who did not have diabetes were assigned to semaglutide 2.4 mg or placebo for 68 weeks, alongside lifestyle changes. The semaglutide group lost 14.9% of body weight on average, versus 2.4% with placebo. (nejm.org) In SURMOUNT-1, tirzepatide produced average weight loss of 15.0% to 20.9% at 72 weeks, depending on dose, compared with 3.1% with placebo. A body-composition substudy found tirzepatide users lost 21.3% of body weight, with fat mass down 33.9% and lean mass down 10.9%; about one-quarter of the weight lost was lean mass. (nejm.org) (ncbi.nlm.nih.gov) That pattern is not unique to one drug. A 2025 narrative review of the literature said clinical trials and real-world evidence “consistently show” that weight reduction with glucagon-like peptide-1 receptor agonists is accompanied by a drop in lean body mass. (ncbi.nlm.nih.gov) Clinicians are increasingly telling patients to treat muscle preservation as part of obesity treatment, not as an afterthought. CED Clinic, in an April 17, 2026 clinical note for prescribers, said resistance training guidance and adequate protein intake counseling should be built into glucagon-like peptide-1 care. (cedclinic.com) The concern is sharper for older adults and people who already have low muscle reserves, a condition called sarcopenia. The same CED Clinic note said lean-mass preservation should shape monitoring decisions and pointed to tools such as dual-energy X-ray absorptiometry, or DEXA, scans rather than relying only on body weight or body-mass index. (cedclinic.com) The weight-loss upside remains large. A 22-trial systematic review covering 41,757 people found semaglutide 2.4 mg and tirzepatide 5 mg, 10 mg, and 15 mg were consistently among the most effective options for weight loss in adults with and without diabetes. (ncbi.nlm.nih.gov) (ajmc.com) The practical message from the evidence is narrower than the hype around the scale: losing weight on these drugs is common, but keeping strength and muscle takes its own plan. (nejm.org) (cedclinic.com)