Card one
The lean-mass share of loss
As a proportion of body weight, lean mass often holds steady or improves during this kind of weight loss, because fat loss dominates. Both things are true at once. Neither one gives the muscle back.
Self-check
How much of your weight loss is muscle?
Sixty seconds, no device, no account. Answer a handful of questions and this page shows you what published trial averages suggest about the lean-mass share of weight loss, what your daily protein floor works out to, and where you stand on the two things that protect muscle.
Everything you enter stays on this page. Nothing is sent anywhere. The arithmetic runs in your browser.
Your read
Every number below is an estimate built from published trial averages and what you entered. None of it is a measurement of your body.
Card two
The protein math
grams a day, your floor at 1.2 g/kg
grams a day at 1.6 to 2.2 g/kg, the range with resistance training
Over 50, the threshold for triggering muscle synthesis rises, so the targets move up with it. The joint advisory puts older adults at 1.6 to 2.3 grams per kilogram of fat-free mass, which sits above the general floor.
For context from the published study: people using a GLP-1 averaged about 54 grams of protein a day against about 62 in non-users, and only 43 percent reached 1.2 g/kg. Ten percent reached 1.6.
Card three
The read
This reads your process, which is the part you control. It says nothing about what your body is actually doing.
These are averages from trials. Your own number is measurable.
Join the ProForta ChallengeThe ProForta Challenge is twelve weeks with your muscle actually measured while you lose the weight. Free, Android-first, fifty places. Your data stays on your own node, and the record of how it went stays yours.
Where these numbers come from
- SURMOUNT-1 body-composition substudy (tirzepatide; about 75 percent of the weight lost was fat and about 25 percent lean mass). Look M, et al. Diabetes, Obesity and Metabolism. 2025. doi:10.1111/dom.16275. PMC11965027
- STEP 1 body-composition exploratory analysis (semaglutide; lean mass down about 9.7 percent against a 19.3 percent drop in fat). Wilding JPH, et al. New England Journal of Medicine. 2021. PMC8089287
- 2025 Joint Advisory on nutrition and muscle preservation, ACLM, ASN, OMA and TOS (adequate protein plus resistance training; the 1.2 g/kg floor, the 1.6 to 2.2 g/kg training range, and the higher older-adult targets). Obesity. 2025. doi:10.1002/oby.24336. PMC12264624
- Protein intake in GLP-1 users (about 54 grams a day against about 62 in non-users; 43 percent reached 1.2 g/kg and 10 percent reached 1.6). Cross-sectional study, Frontiers in Nutrition. 2025. Frontiers in Nutrition
This self-check is a wellness tool. It does not diagnose anything, it is not a measurement, and it gives no advice about medication, dose, or treatment. Questions about your medication belong with your clinician, who stays the decision-maker.