GLP-1 muscle answer
A peer-reviewed Geebs Science answer on GLP-1 medications, protein, resistance training, lean mass, strength, and practical muscle-preservation steps.
Kris Oddo, NASM-certified personal trainer, is the founder and head coach of Gains From Geebs (Geebs Coaching), a 1:1 online fitness coaching practice.
Short answer
Usually, yes. About a quarter of the weight lost on these medications is lean mass, and lifting plus enough protein is the best tool for keeping it. While clinicians manage the medication, the training plan should protect muscle, strength, and function. Protein and resistance training are not optional details when appetite and body weight are changing fast.
How strong is this kind of study?
Randomized controlled trial protocol. Heavier plates are built from more studies, so they move less when the next one lands.
By Kris Oddo, NASM-CPT · Updated
About a quarter of it is lean mass. In the SURMOUNT-1 body-scan substudy, people on tirzepatide lost 21.3% of their bodyweight over 72 weeks, and about 75% of what they lost was fat and 25% was lean mass.
The placebo group, who lost far less, had the same 75/25 split. That is the honest reading: the medication did not single out muscle, but it made the total so large that the lean share is a real amount of tissue.
Lean mass on a scan is not only muscle (it includes water and organs), which is another reason to track strength alongside the scan.
Source: Look et al., 2025, Diabetes, Obesity and Metabolism (PMID 39996356)
It is the best tool there is, though direct GLP-1 trials are still running. A 2024 review in Diabetes Care put incretin-drug lean-mass loss at about 10%, or 6 kg, and found supervised lifting for over 10 weeks adds about 3 kg of lean mass.
The same review found strength gains of about 25% from that kind of training, in men and women, and its authors recommend tailored resistance training alongside these medications.
A trial testing protein plus lifting during semaglutide and tirzepatide treatment (LEAN-PREP) has published its protocol but not its results, so nobody can yet promise a number. Lifting is still the safe bet while the evidence comes in.
Source: Locatelli et al., 2024, Diabetes Care (PMID 38687506)
Resistance training and enough protein. A 2025 joint advisory from four obesity and nutrition societies lists muscle and bone loss among the main problems with GLP-1s, and preserving them through resistance training and diet as a priority.
It also lists a check of muscle strength, function and body composition at the start of treatment among its priorities, and notes these medications cut weight by 5% to 18% in trials, and that many people stop taking them and regain weight. Muscle you keep on the way down is muscle you still have if that happens.
Nothing here is dosing advice. Starting, stopping or changing a medication belongs with your prescriber.
Source: Mozaffarian et al., 2025, Obesity, joint advisory of four societies (PMID 40445127)
Try this
Track three things alongside body weight: weekly hard sets, daily protein hit rate, and strength on a few key lifts. If appetite is too low to hit protein, bring that to the clinician and adjust the meal structure.
Honest limits
GLP-1 dosing, side effects, contraindications, and whether medication is appropriate belong with qualified clinicians.
Weekly Science Drop
One useful study, Kris's coaching move, and the honest limit that keeps the claim honest.
Free coaching tip
Want a useful coaching tip before you go?
Studies behind this answer
A GLP-1 can reduce appetite, but the nutrition plan still has to protect protein, micronutrient quality, training fuel, and long-term routines.
If your appetite is suppressed, the challenge can shift from eating less to eating enough nutrient-dense food often enough.
This study will test whether resistance exercise and protein can protect muscle during GLP-1-supported weight loss, but results are not available yet.
Rapid weight loss deserves strength and protein support, but evidence does not show that GLP-1 use automatically destroys muscle.
Free weekly email
One study, one answer, and one honest limit so research becomes a usable next action.
Free coaching tip
Want a useful coaching tip before you go?
FAQ
Weight loss and body composition are not the same thing. The plan still needs strength training, protein, and recovery if function and muscle matter.
Smaller protein-forward meals, easier textures, and planned timing may help. If symptoms or low intake continue, involve the prescriber or another qualified clinician.
Not necessarily. The first target is keeping consistent, recoverable strength work in the week, not proving toughness while intake and weight are changing.
Keep going
25 lbAverage fat loss across 15 completed clients tracked over 16 weeks. Individual results vary.
1 of 3
2 months coached“I've lost 10 lb, which has definitely given me more confidence. I'm not as tired during work and I can lift things easier than before.”
See the full story
6 months coached“Before I couldn't do a single pull-up, and now I can do five all on my own.”
See the full story
3 months coached“Kris changed the way I view my life. Even though I do not have much free time, he helps me push myself to keep going and never lets me give up.”
See the full storyWays to work with Kris
You have read the argument. These are the options, and whichever one you pick carries into the application.
1 of 5
Most hands-onYou want a coach on training, food and accountability every day.
Core 1:1You want a coach with you daily, without the concierge layer.
New, self-drivenYou run your own week and want a coach reading the numbers.
One-time guidanceYou want direction now without a monthly commitment.
Community membershipYou want a serious fitness community without a coaching contract.