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, the daily protein target the 2025 joint advisory gives, 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, the advisory's simple target when you have no body scan
grams per kilogram of fat-free mass a day, its more accurate target once a scan gives you that number
Over 50, the advisory names older age among the things that raise the risk of muscle loss when protein intake is low, which makes reaching the target matter more. It gives no separate protein figure for older adults, so the target above stands.
The advisory also says prolonged intake above 2 grams per kilogram a day should be avoided.
For context from a published study of 69 people using a GLP-1: protein intake averaged about 77 grams a day, and measured against adjusted body weight, 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, a small beta. Your data stays on your own node, and the record of how it went stays yours.
Share your read
Sharing is yours to start, never automatic. The link opens a card with the band above and the protein figure your read was measured against, and carries nothing else you entered on this page.
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 nutritional priorities to support GLP-1 therapy, ACLM, ASN, OMA and TOS (adequate protein plus resistance training; 1.5 g per kg of fat-free mass a day as the more accurate target, an absolute target of 80 to 120 g a day, and a caution against prolonged intake above 2 g/kg a day). Obesity Pillars. 2025;15:100181. doi:10.1016/j.obpill.2025.100181. PMC12264624
- Protein intake in GLP-1 users (69 people; about 77 grams a day on average; measured against adjusted body weight, 43 percent reached 1.2 g/kg and 10 percent reached 1.6). Johnson B, et al. Cross-sectional study, Frontiers in Nutrition. 2025. doi:10.3389/fnut.2025.1566498. Frontiers in Nutrition
Each of these is unpacked, one question per page, in the ten guides on muscle and weight loss.
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.