Muscle Loss Risk Estimator
Lose weight carelessly on a GLP-1 and a real share of it can come from muscle. Enter how much you plan to lose to see an illustrative band, and how much protein plus lifting may protect.
Read this as a range, not a verdict.
These bands come from group averages in GLP-1 trials. Research suggests this pattern, but it is not a prediction about you. Your real result depends on your protein, your training, and your own physiology, which is exactly what Myo helps you track.
Lean mass at risk without intervention
7.5to12lb
Roughly 25 to 40 percent of weight lost came from lean mass across major trials (about 25 percent in SURMOUNT tirzepatide data, up to about 40 percent in STEP and SUSTAIN semaglutide analyses). Definitions vary.
Lean mass at risk with protein plus lifting
1.5to4.5lb
Research suggests adequate protein plus resistance training 2 to 4 times a week preserves a large majority of lean mass during weight loss. This reduced band is illustrative and clearly hedged, not a guarantee.
How this works
This tool multiplies your planned weight loss by the share that tends to come from lean mass, based on group averages in GLP-1 trials. Without deliberate muscle protection, that share has landed somewhere around 25 to 40 percent: roughly 25 percent in tirzepatide (SURMOUNT) data and up to about 40 percent in some semaglutide (STEP and SUSTAIN) analyses. Definitions and methods differ between studies, so it is a range, not a single number.
lean mass at risk = planned loss x lean-mass share
The second band shows a substantially smaller share. Research suggests that adequate protein plus resistance training two to four times a week preserves a large majority of lean mass during weight loss. We present that as a reduced, clearly hedged band rather than a promise.
Read this as research, not a prediction about you. Individual results vary widely, and the only way to know what is happening in your own body is to track it. That is Myo's whole thesis. To act on it, read the complete guide to GLP-1 muscle loss, resistance training for GLP-1 users, and how much protein you need.
Frequently asked questions
Is this a prediction of how much muscle I will lose?
No. It is an illustrative band drawn from group averages in GLP-1 trials, not a prediction about you. Individual results vary widely. Track your own body composition to see what is actually happening.
Where does the 25 to 40 percent figure come from?
Across major GLP-1 trials, lean mass made up a meaningful share of total weight lost, with estimates often cited around 25 percent in tirzepatide (SURMOUNT) data and up to roughly 40 percent in some semaglutide (STEP and SUSTAIN) analyses. Methods and definitions differ, so treat it as a range.
Can I really protect that much muscle?
Research suggests adequate protein plus resistance training two to four times a week preserves a large majority of lean mass during weight loss. It is not a guarantee, but the direction of the evidence is strong and consistent.
Related tools
Related reading
Track it, do not just calculate it
Get all of this, plus fat-vs-muscle tracking, in the app
Myo brings these calculators together with your shots, protein, training, and body composition, so you can see whether you are losing fat or muscle, not just guess at the math.