GLP‑1s can cost muscle without care
Multiple outlets report that people who stop GLP‑1 weight‑loss drugs without keeping up diet and resistance training often regain weight as fat rather than muscle, which can worsen insulin resistance in some cases (theweek.in). Nutrition advice emphasizes maintaining adequate protein, fiber, and micronutrients during GLP‑1‑induced appetite loss, and researchers have also flagged genetic variants that may change side effects and outcomes on these drugs ( ). Separately, biotech firm NorthStrive announced it has an EL‑32 working cell bank and has begun manufacturing optimization for a dual‑myostatin program aimed at preserving lean muscle during GLP‑1 therapy (manilatimes.net).
Glucagon-like peptide 1 drugs can cut body weight fast, but without enough protein and strength training, some of that loss is muscle. (pmc.ncbi.nlm.nih.gov) These medicines work by slowing stomach emptying and lowering appetite, so people often eat much less than before. A joint 2025 advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society said nutrition support during treatment should prioritize protein, fiber, fluids, and micronutrients. (pmc.ncbi.nlm.nih.gov) Body-scan data from the SURMOUNT-1 substudy found tirzepatide users lost 21.3% of body weight by week 72, including 33.9% of fat mass and 10.9% of lean mass. About 75% of the weight lost was fat mass and 25% was lean mass. (pmc.ncbi.nlm.nih.gov) The risk does not end when the prescription stops. In the STEP 1 extension, people who discontinued semaglutide regained 11.6 percentage points of lost weight within a year, or about two-thirds of their prior weight loss, and cardiometabolic improvements also drifted back toward baseline. (pmc.ncbi.nlm.nih.gov) Doctors and dietitians are focusing on body composition, not just the scale, because muscle helps regulate glucose disposal and resting energy use. A 2025 review in *Acta Diabetologica* said muscle loss can worsen insulin resistance and functional decline in people with obesity and diabetes. (springer.com) That is why obesity specialists pair these drugs with resistance exercise and higher protein targets. The Obesity Society’s lean-mass guidance recommends resistance training two to three times a week and protein intake of 1.2 to 1.6 grams per kilogram per day during active weight loss. (neobesitysociety.org) Nutrition advice is getting more specific as appetite loss becomes a bigger practical problem. Business Insider reported on April 14 that nutritionist Rob Hobson said meals on these drugs should be built around high-quality protein, fiber, and nutrient-dense foods because low appetite can make it hard to meet basic needs. (businessinsider.com) Researchers are also starting to explain why one patient loses more weight while another gets more nausea or vomiting. A *Nature* paper published April 8 identified common variants near GLP1R and GIPR associated with differences in weight-loss response and gastrointestinal side effects from these medicines. (nature.com) Drugmakers and smaller biotechs are now chasing add-ons meant to protect lean mass during treatment. NorthStrive Biosciences said on April 13 that it moved its EL-32 working cell bank to a United States fermentation facility and started manufacturing optimization for a dual-myostatin program aimed at muscle preservation alongside glucagon-like peptide 1 therapy. (pmgcholdings.com) The current message from clinicians is narrower than the hype around the drugs: keep the medicine supervised, keep protein intake up, and keep lifting. The weight on the scale can come back, but rebuilding lost muscle is slower. (pmc.ncbi.nlm.nih.gov)
