Strength Training on GLP-1 Medications: How to Keep Your Muscle
If you're losing weight on a GLP-1 medication, some of what comes off is lean mass, not just fat. Strength training two or three times a week and eating enough protein are the two things most linked with keeping your muscle while the scale goes down. Start light, because eating less often means less energy, and plan both with the person who prescribes your medication.
Exercise for weight management is number 3 in the ACSM's 2026 fitness trends, and it now includes people on medications like GLP-1s. This guide covers the training side only. Anything about the medication itself is a conversation for your doctor.
How much of the weight lost is muscle?
Weight loss is never pure fat. Researchers measure this with DXA scans, which split your body into fat mass and lean mass (muscle, plus water, organs and other tissue).
- STEP 1 (semaglutide). A 2025 joint advisory from four US nutrition and obesity groups, looking back at the trial's DXA scans, reports that of an average 13.6 kg (30 lb) lost, 8.3 kg was fat and 5.3 kg, about 38%, was lean mass.
- SURMOUNT-1 (tirzepatide). In the trial's body composition substudy, about 75% of the weight lost was fat and about 25% was lean mass. The placebo group, who lost much less, lost it in the same 75 to 25 split.
That last point matters: losing some lean mass happens with most weight loss, not just on these drugs. And lean mass isn't all muscle, so true muscle loss is smaller than these numbers. Still, muscle keeps you strong and steady on your feet, and after 40 it's harder to win back than to keep.
What helps you keep it
Lifting. A meta-analysis of 6 trials in older adults with obesity found that adding resistance training to a calorie-cut diet prevented about 93.5% of the lean mass loss that dieting alone caused. They trained three times a week for 12 to 24 weeks. They weren't on GLP-1s, but the idea holds: give your muscles work and your body has a reason to keep them.
The joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society says these medications should come with a structured exercise program, aiming for strength training at least 3 times a week. It also notes that walking and other aerobic exercise on their own do less to preserve lean mass.
Protein. The same advisory lists adequate protein alongside strength training as one of its priorities. It notes the general allowance is 0.8 g per kg of bodyweight a day, and that higher targets, such as 1.2 to 1.6 g/kg, have been proposed during weight loss. For someone at 180 lb (82 kg), that's roughly 100 to 130 g a day. Set your own number with your prescriber or a dietitian, especially if your appetite is very low.
Training when you're eating less
A smaller appetite usually means fewer calories, and that can mean less energy in the gym. Plan for it.
- Start lighter than you think. Pick weights that leave 3 or 4 good reps in the tank for the first few weeks.
- Keep sessions short. Four or five exercises, about 45 minutes. Quality over quantity.
- Eat something with protein before you train if you can, even something small like Greek yogurt.
- Stop if you feel dizzy, faint or sick. Sit down, and tell your prescriber about it.
Holding your strength steady while you lose weight is a win. Getting stronger is a bonus.
What to train
Big, simple movements: a squat, a hinge (like a Romanian deadlift), a push, a pull and a carry or core move every session. Machines and dumbbells are fine. For why this still works later in life, read the science of training after 40.
How to start if you're coming back
- Week 1. Two sessions, two sets per exercise, easy weights. Learn the moves and see how your energy holds up.
- Week 2. Three sessions, two sets each. Walk 20 minutes on one or two other days.
- Week 3. Three sessions, three sets each. Nudge the weights up only if every set felt easy.
- Week 4. Same as week 3. Tell your prescriber how training and energy are going.
Here's how many days a week to lift, and why more isn't better.
A week of strength training on a GLP-1
Three short strength days, easy walks in between, and real rest. On a low-energy day, a lighter session or just the walk is fine.
| Day | Session | How long |
|---|---|---|
| Monday | Full Body A | About 45 min |
| Tuesday | Easy walk | 20 to 30 min |
| Wednesday | Full Body B | About 45 min |
| Thursday | Easy walk or mobility | 20 to 30 min |
| Friday | Full Body C | About 45 min |
| Saturday | Longer walk | 30 to 45 min |
| Sunday | Rest |
Full Body A, B and C each cover a squat, a hinge, a push, a pull and a carry or core move, in about 45 minutes.
Keep the muscle, free
Three short sessions a week give your body a reason to keep its muscle while the weight comes off. Full Body, 3 days is free in Liftspan: it's built for your equipment and around any joint you flag, every weight is set for you and moved up as you earn it, and each block ends with a lighter deload week. Rather use paper? Download the sheet.
Common questions
Do GLP-1 medications cause muscle loss?
Most weight loss includes some lean mass, and GLP-1 trials are no different. In the trials' DXA scans, roughly a quarter to a little under 40% of the weight lost was lean mass, which includes water and organs as well as muscle. Strength training and enough protein are linked with keeping more of it.
How often should I lift weights on a GLP-1?
A 2025 joint advisory from four US nutrition and obesity groups suggests aiming for strength training at least 3 times a week. If that's too much at first, start with two sessions and build up.
How much protein do I need on a GLP-1?
The same advisory notes that targets of 1.2 to 1.6 g per kg of bodyweight a day have been proposed during weight loss. Your needs depend on your health and your appetite, so agree a number with your prescriber or a dietitian.
Is walking enough to keep my muscle?
Walking is great for your heart and your habit, but on its own it does less to preserve lean mass than strength training. Do both: walk on the days between your strength sessions.
Using Liftspan? See how Liftspan sets your weights and moves them up in the help manual. New to it? Liftspan is a strength training app for lifters over 40 that builds your plan around your joints and moves the weight for you.
Sources: Mozaffarian et al. 2025, Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from ACLM, ASN, OMA and TOS (American Journal of Clinical Nutrition) · Look et al. 2025, Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study (Diabetes, Obesity and Metabolism) · Sardeli et al. 2018, Resistance training prevents muscle loss induced by caloric restriction in obese elderly individuals (Nutrients) · ACSM top fitness trends for 2026. General information, not a substitute for a clinician.
Keep reading: the science of training after 40 · how many days a week to lift after 40 · longevity training · how much protein you need after 40 · how to start working out again after a long break · all guides