Peer-reviewed study
Tirzepatide changes fat and lean mass
Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight
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.
Quick answer
What this study found
Weight loss supported by medication still needs the basics: lift, eat enough protein, track strength, and keep the goal bigger than scale loss.
How strong is this kind of study?
- Reviews of many studies
- Controlled trialsThis study
- Observational
- Narrative reviews
Randomized trial body-composition analysis. Heavier plates are built from more studies, so they move less when the next one lands.
At a glance
What kind of study this is
Strong evidence
A controlled trial, where people were randomly assigned. That is the design that can actually show cause rather than coincidence.
- Design
- Randomized trial body-composition analysis
- Published
- 2025
- Journal
- Diabetes, Obesity and Metabolism
- Reference
- PMID 39996356
Honest limits
What this study does not prove.
Group-level body-composition results are not individual medical advice. Medication and side-effect decisions belong with your prescriber.
Kris's practical takeaway
Here's what to do with it.
Weight loss supported by medication still needs the basics: lift, eat enough protein, track strength, and keep the goal bigger than scale loss.
If you are losing weight
What this means if you're losing weight.
On a GLP-1, about a quarter of the weight that comes off is lean mass. Lifting and enough protein are what you control: they decide how much of the rest is fat. The medication stays with your prescriber.
Ways to use it
Safe ways to apply it.
Fast weight loss needs a muscle plan
Lower appetite does not replace strength and nutrition
Track strength, not just scale weight
Related questions
Questions this research helps answer.
GLP-1 and lean mass answer
Do GLP-1s cause muscle loss?
GLP-1s can produce major weight loss, and body-composition studies show that some lean mass can change during that process. The practical takeaway is not panic. It is to make strength training, protein, steps, and function tracking non-negotiable while medical care stays with the prescriber.
GLP-1 training answer
Should you lift while on a GLP-1?
For most people pursuing better body composition, lifting becomes more important when appetite and scale weight are dropping. Resistance training gives the body a reason to keep strength and muscle while nutrition supports recovery.
Related guides and studies
Keep learning about peptides.
FAQ
Quick questions
What is the practical takeaway from this study?
Weight loss supported by medication still needs the basics: lift, eat enough protein, track strength, and keep the goal bigger than scale loss.
What does this study not prove?
Group-level body-composition results are not individual medical advice. Medication and side-effect decisions belong with your prescriber.
Weekly Science Drop
Get one useful study each week.
One study, one coaching move, and one honest limit so research turns into action instead of overclaiming.
Free coaching tip
Want a useful coaching tip before you go?
Keep going
25 lbAverage fat loss across 15 completed clients tracked over 16 weeks. Individual results vary.
1 of 3
2 months coachedDown 10 pounds and carrying more confidence into daily life.
Justin · 24 · 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 coachedFrom zero pull-ups to five on his own.
Jon Miller · 27 · 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 coachedBetter technique, better health, and support to keep going.
Jhoan Rincon · 46 · 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
Pick the one that fits your week.
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.- Daily replies, usually within the hour
- FaceTime meal prep: cook, portion, freeze the week
- Fully custom plan with Kris's own demo videos
Core 1:1You want a coach with you daily, without the concierge layer.- Custom training plan with demo videos
- Macros-based nutrition, no rigid meal plan
- Daily accountability at standard priority
New, self-drivenYou run your own week and want a coach reading the numbers.- Custom training and nutrition plan
- One recorded Loom review of your week
- Adjustments based on what the week showed
One-time guidanceYou want direction now without a monthly commitment.- A focused 45-minute Zoom with Kris
- A real diagnosis of what is holding back progress right now
- Guidance on training, nutrition, accountability, or schedule
Community membershipYou want a serious fitness community without a coaching contract.- Access to the Titan Forge Science-Based Telegram community
- Training, nutrition, recovery, and research discussion
- Shared accountability with like-minded lifters