You have probably heard that GLP-1 drugs like Ozempic and Mounjaro melt off pounds fast.
What they take with them is talked about less. For many users, a slice of the weight lost is not fat at all.
A randomized controlled trial published November 9 in Nature Medicine tested resistance training in adults taking tirzepatide.
Those who lifted weights three times a week lost 25 percent less lean tissue than those who relied on the drug alone.
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The trial, called T-REx, ran for 40 weeks. Both groups shed around 22 kilograms (roughly 49 pounds). But their bodies looked very different at the end.
Participants who skipped the weights lost about 10 percent of their upper and lower body strength. The trained group gained 10 percent.
Why muscle loss on these drugs matters
Semaglutide is the active ingredient in Novo Nordisk's Ozempic and Wegovy. Tirzepatide is the active ingredient in Eli Lilly's Mounjaro and Zepbound. Both work by curbing appetite and slowing digestion.
The result is rapid weight loss. But lean tissue, including muscle, tends to drop along with the fat.
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In older adults, that can mean weaker legs, poor balance and trouble climbing stairs.
"Loss of lean mass, including muscle, is an inevitable part of weight loss by any method," said Danny Green, the trial's lead investigator. Green is Winthrop Professor at the University of Western Australia.
What the resistance training looked like
The 120 volunteers were men and post-menopausal women aged 50 to 70. All had obesity, or were overweight with a weight-related health condition, and all took tirzepatide.
Half of them added three resistance training sessions a week. Resistance training means forcing the muscles to work against a load, with free weights, gym machines or elastic bands.
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The researchers tracked body composition every eight weeks using DEXA body scans, along with upper and lower body strength tests.
What it means for GLP-1 users at home
Prescriptions for tirzepatide and semaglutide have climbed into the millions worldwide. Muscle loss has been a worry since the drugs entered mainstream use, especially for people over 50.
The T-REx findings point to a concrete fix. Three sessions a week, covering both upper and lower body, held onto lean tissue and built strength on top of a 22-kilogram drop in weight.
Anyone on a GLP-1 who is new to the gym, or who lives with joint, heart or back problems, should talk to their doctor before starting a weight-training program.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.