GLP-1 medications like Ozempic, Wegovy, Rybelsus, Mounjaro and Zepbound have changed the weight-loss conversation. They suppress appetite and slow digestion, and the results on the scale can be dramatic. But there is a catch that gets far less attention than the before-and-after photos: a meaningful share of the weight you lose on a GLP-1 can be lean muscle, not just fat. This guide explains why that matters, what the evidence says, and how to train so the number on the scale reflects real, durable results. It is general information, not medical advice.
The muscle problem nobody mentions
Any rapid weight loss, whether from dieting, surgery or medication, tends to cost some muscle along with fat. GLP-1 drugs are no exception. A 2026 systematic review and meta-analysis in the International Journal of Obesity found that roughly 20 to 30 percent of the total weight lost on GLP-1 receptor agonists can come from lean mass. The drugs do reduce fat more than muscle, and functional strength often holds up, but the lean-mass loss is real and worth planning around, especially for older adults for whom muscle is already at a premium.
Why care? Muscle is metabolically active tissue. Lose too much of it and your resting metabolism drops, which makes weight easier to regain and harder to lose next time. Muscle is also what keeps you strong, mobile and injury-resistant as you age. Losing fat is the goal; losing the muscle underneath it is a side effect to defend against.
Discontinuation and regain: the field's number-one problem
The other hard truth is what happens when people stop. GLP-1 medications manage weight while you take them; they are not a one-time cure. Studies of semaglutide and tirzepatide consistently show that a large portion of lost weight returns in the months after discontinuation. If some of the original loss was muscle and the regain is mostly fat, body composition can end up worse than where it started.
This is exactly where behavior does the heavy lifting. The clinical consensus is straightforward: resistance training plus adequate protein preserves muscle during treatment and helps sustain results afterward. The medication changes appetite; your habits decide what you keep.
What the evidence says to actually do
Two levers do most of the work, and they reinforce each other:
- Resistance training. Lifting, bodyweight strength work and progressive overload signal your body to hold onto muscle even in a calorie deficit. Aim for two to four strength sessions a week hitting all major muscle groups. Pairing GLP-1 treatment with structured resistance training and higher protein intake has been shown to preserve substantially more lean mass than medication alone, so more of the weight you lose comes from fat rather than muscle.
- Protein. With appetite suppressed, it is easy to under-eat protein badly. Research-backed targets land around 1.2 to 2.0 grams of protein per kilogram of body weight per day. Prioritize protein at every meal so your muscles have the raw material to rebuild.
Add daily movement, walking and steps, on top of structured strength work, and you have the full recipe. None of this changes how the drug works. It changes what your body does with the weight loss the drug makes possible.
How Cadoo helps you actually do the work
Knowing you should strength-train is easy. Doing it two to four times a week, every week, for months, while your appetite is gone and motivation dips, is the hard part. That is the exact gap Cadoo is built for. Cadoo lets you stake money with friends on hitting your fitness goals, so accountability comes from real stakes and a group chat instead of willpower alone.
- Verified strength work: your phone's camera counts and form-scores bodyweight reps like squats and pushups, so a workout only counts when you actually do it.
- Steps and movement: steps and distance sync from Apple Health and Google Health Connect, so daily activity counts toward a game automatically.
- Consistency over months: recurring weekly challenges keep you training through the long stretch when results depend on showing up.
Cadoo does not change your medication or its effects in any way, and it will never encourage you to start a drug. Its only job is to help you put in the exercise that preserves muscle and protects your results.
A note before you start
GLP-1 medications are prescription-only and are not right for everyone. Talk to your doctor or clinician before starting, stopping or changing any medication or exercise program, especially if you have existing health conditions. Individual results vary, and this article is general information, not medical advice. Cadoo is not affiliated with, endorsed by or sponsored by any drug manufacturer; brand names are the trademarks of their respective owners and are used here editorially.
Frequently asked questions
Can you exercise while taking a GLP-1 medication?
Yes, and most clinicians actively recommend it. Resistance training plus adequate protein is the best-supported way to preserve lean muscle during GLP-1 weight loss and to sustain results after you stop. Start gradually, stay hydrated, and clear any new program with your doctor first.
Do GLP-1 drugs cause muscle loss?
They can. A 2026 meta-analysis in the International Journal of Obesity found roughly 20 to 30 percent of the weight lost on GLP-1 receptor agonists can come from lean mass. The drugs reduce fat more than muscle, but strength training and protein are what protect the muscle you keep.
What are the best workouts on a GLP-1?
Prioritize resistance training two to four times a week covering all major muscle groups, paired with daily steps and movement. Progressive strength work signals your body to hold onto muscle even in a calorie deficit, which protects your metabolism and your long-term results.
Why do people regain weight after stopping a GLP-1?
GLP-1 medications manage weight while you take them; appetite and weight often rebound after discontinuation. Building muscle and consistent exercise habits during treatment gives you a metabolic and behavioral foundation that makes results more durable once the medication stops.
