A promising new drug could help people taking popular weight-loss medications like Mounjaro preserve muscle while shedding fat, potentially addressing one of the biggest concerns linked to rapid weight loss. Researchers say the experimental treatment, called apitegromab, may reduce the muscle loss often seen with GLP-1 weight-loss drugs, including Mounjaro and Wegovy.
The findings, published in the prestigious journal Nature Medicine, suggest that combining apitegromab with Mounjaro could help patients achieve healthier weight loss by protecting lean muscle mass without affecting overall weight reduction.
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Why does muscle loss matter during weight loss?
GLP-1 receptor agonists such as Mounjaro (tirzepatide), Wegovy, and Ozempic have revolutionized obesity treatment by helping people lose significant amounts of weight. These medications work by reducing appetite and helping users feel full for longer.
However, experts have raised concerns that as much as one-third of the weight lost on these medications may come from muscle rather than fat. Unlike fat, muscle tissue is much harder to rebuild once it is lost. Loss of muscle mass can affect strength, mobility, metabolism, and long-term health. It has also been linked to changes in body shape, including the so-called “Ozempic butt” phenomenon, where rapid weight loss leads to a sagging or flattened appearance due to reduced fat and muscle volume.
What is apitegromab?
Apitegromab is an experimental drug currently being tested in clinical trials. It works by blocking a protein involved in muscle breakdown, helping the body preserve lean muscle tissue during periods of rapid weight loss.
The drug is currently administered through intravenous infusion, although researchers are exploring the possibility of a self-injectable version similar to existing obesity medications. Beyond weight management, apitegromab is also being investigated as a treatment for muscle-related disorders such as spinal muscular atrophy.
What did the study find?
The six-month clinical trial involved 102 adults, most of whom were women, who were taking Mounjaro for obesity treatment.
Researchers found that participants who received apitegromab alongside Mounjaro retained approximately 1.9 kilograms more muscle mass than those receiving a placebo. The study showed that lean mass accounted for only 14.6 per cent of total weight loss in the apitegromab group, compared with 30.2 per cent in the placebo group. Importantly, both groups lost similar amounts of overall weight, indicating that the drug helped preserve muscle without reducing fat loss effectiveness.
Experts urge caution
While the findings are encouraging, researchers stress that more studies are needed before apitegromab becomes a routine treatment for people using GLP-1 weight-loss medications.
Experts say larger and longer-term trials will be necessary to determine whether preserving muscle mass leads to measurable improvements in strength, physical function, quality of life, and long-term health outcomes. The treatment may be particularly beneficial for individuals who experience rapid muscle loss while taking obesity medications, though it may not be necessary for every patient.
How to protect your muscles while losing weight?
Until new treatments become widely available, experts recommend combining GLP-1 medications with lifestyle strategies that support muscle health.
Strength training at least twice a week can help maintain muscle mass. Activities such as lifting weights, resistance band exercises, cycling, stair climbing, yoga, squats, and even heavy gardening can contribute to muscle preservation. Diet also plays a crucial role. Consuming adequate protein, typically 20 to 40 grams per meal, can help maintain or build muscle. Good protein sources include lean meat, fish, eggs, dairy products, beans, lentils, chickpeas, nuts, and high-protein yogurts.
As obesity treatments continue to evolve, apitegromab may represent an important step toward helping patients lose fat while preserving the muscle needed for long-term health and mobility.