Strength Training On A GLP-1 Medicine: What The Research Shows

Short Answer

In a 160-adult body-composition substudy of tirzepatide, about 75% of the weight lost was fat and about 25% was lean mass, the same split as on placebo, and a 2024 review proposes tailored lifting to protect that lean mass. None of the studies on this page tested a lifting plan in people taking these medicines, so lifting is the sound next step, not a proven fix. Your prescriber decides your medicine; a coach builds the training around it.

Updated 7 October 2026

How much of the weight lost on a GLP-1 medicine is lean mass?

A body-composition substudy of the SURMOUNT-1 trial (Look and colleagues, 2025, PMID 39996356) scanned 160 adults with DXA at the start and at week 72. On tirzepatide, body weight fell 21.3%, fat mass 33.9% and lean mass 10.9%. On placebo the falls were 5.3%, 8.2% and 2.6%. Of the weight lost, about 75% was fat and 25% was lean mass, in both groups, and the split stayed consistent across most of the subgroups checked: women and men, and three age bands (under 50, 50 to under 65, and 65 and over).

Two cautions. The substudy was 160 of the 2,539 people in the trial, 73% of them women, with a mean BMI of 38. And a DXA scan estimates lean soft tissue; a 2026 trial (PMID 42668016, 46 people) found that drinking 1,000 mL of water raised the whole-body estimate, so the figure is not a direct count of muscle.

How much weight do these medicines take off?

In the STEP 1 trial (Wilding and colleagues, New England Journal of Medicine, 2021, PMID 33567185), 1,961 adults with overweight or obesity and no diabetes were assigned 2 to 1 to once-weekly semaglutide or placebo, plus lifestyle support, for 68 weeks. Mean body weight changed by -14.9% on semaglutide and -2.4% on placebo, a difference of 12.4 percentage points.

Weight loss of 5% or more was reached by 86.4% of the semaglutide group and 31.5% of the placebo group. At that scale, even a modest share of lean mass is a real amount, which is why the next section matters. The trial was funded by the drug maker, and its main endpoint was body weight, not muscle.

Why does losing lean mass matter?

A narrative review in Diabetes Care (Locatelli and colleagues, 2024, PMID 38687506) states that incretin medicines induce roughly 15 to 24% weight loss, and that they also cause rapid and significant loss of lean mass, about 10% or about 6 kg, which the authors compare to a decade or more of aging.

The same review notes that maintaining muscle mass and function as people age is crucial to avoiding sarcopenia and frailty, which are strongly linked to illness and death. It also proposes that retaining lean mass during treatment could blunt weight regain when treatment stops. That is a proposal, not a tested result. It is a narrative review, so it summarises other studies rather than reporting a new trial.

Does lifting help someone taking a GLP-1 medicine?

The same 2024 review reports that supervised resistance training lasting more than 10 weeks can raise lean mass by about 3 kg and strength by about 25% in men and women. That figure comes from studies of people in general, not from people on these medicines.

The closest trial is Lundgren and colleagues (New England Journal of Medicine, 2021, PMID 33951361): 195 adults with obesity, after an 8-week low-calorie diet, were assigned for a year to exercise, liraglutide, both, or placebo. The combination lowered body-fat percentage by 3.9 points, about twice the 1.9 points with liraglutide alone and the 1.7 points with exercise alone. The exercise was a moderate-to-vigorous program, not a lifting plan specifically.

How big a deficit you can run without losing muscle

What do clinical groups recommend about muscle on these medicines?

A joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society (Mozaffarian and colleagues, 2025, PMID 40450457) lists muscle and bone loss among the challenges of GLP-1 treatment, next to side effects, nutrient shortfalls and weight regain.

It calls for a baseline exam that includes muscle strength, function and body composition, and for preserving muscle and bone mass through resistance training and an appropriate diet during treatment. Corrections to the advisory have since been published, so we quote only these headline points from the abstract. The advisory is written for clinicians; it does not give a lifting program.

What does a coach add, and what stays with your prescriber?

Your prescriber decides whether you take a medicine, at what dose, and when to stop. A coach does not. Titan Forge coaches training, nutrition and accountability, and its published stance is assessment first, a plan built around real constraints, then weekly check-ins that adjust the plan from measured trends.

If you take a GLP-1 medicine, say so when you apply; Steve "Doc" Ginevan, PhD reviews your goal, training history and schedule before any call. Coaching is online worldwide and in person at 9780 S Meridian Blvd, Englewood, CO 80112. Standard coaching is $400/mo and nutrition-only coaching is $200/mo. The pricing page has the full list.

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Titan Forge Fitness provides fitness and nutrition coaching. It is not medical care, and nothing here diagnoses, treats, or replaces advice from a physician, pharmacist or registered dietitian. It does not advise starting, changing or stopping any medicine. If you take a prescription medicine or have a medical condition, get clinical clearance before starting or changing a training program.