The app that tells you if you’re losing fat or muscle
The scale says you lost 10 pounds. It doesn’t say what they were made of.
Short answer
ProgressLens tells you whether you’re losing fat or muscle. Its AI Progress Report includes a muscle-loss signal: it compares how fast your waist is shrinking with your arms and shoulders, checks your weekly rate of weight loss, and reads your matched photos. If your limbs shrink as fast as your waist while weight drops quickly, it flags it and tells you what to do.
How the muscle-loss signal works
When you lose mostly fat, your waist shrinks much faster than your arms and shoulders. When you lose muscle too, your arms and shoulders shrink almost as fast. ProgressLens tracks both over 4 to 8 weeks, adds your weekly weight change, and shows one of these states:
| State | What it means |
|---|---|
| On track | Your waist is shrinking faster than your arms and shoulders: mostly fat loss. |
| Watch | Your arms and shoulders are shrinking too. Keep lifting and keep protein high. |
| Possibly losing muscle | Limbs shrinking as fast as the waist while weight drops quickly. Slow down, prioritise strength training and protein. |
| Not enough data yet | Log weight, waist and arms or shoulders a few weeks apart to turn it on. |
Your progress reportWhere you are
16–18%
Estimated body fat · medium confidence
- From photos: 15–19%
- From tape measurements: 17.2%
What changed
Weight −3.1 lbWaist −0.8 in
- Waist: more defined
- Abs: more defined
- Shoulders: unchanged
Is it working
On track
Your waist is shrinking faster than your arms and shoulders: mostly fat loss.
What to do next
Cut
- Lose 0.7–1.1 lb a week
- About 12 weeks to around 12% body fat
- Next check-in in about two weeks, in the same place and light.
Estimates from your photos and measurements, not a medical assessment.
Built for GLP-1 journeys
On semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound), weight can drop fast, and clinical substudies with DXA scans found that roughly 25–40% of the weight lost was lean mass. Tell ProgressLens you’re on a GLP-1 in the About you step and the report puts the fat vs muscle check first and reminds you to talk to your clinician about protein and strength training. It doesn’t track doses and isn’t medical advice.
What to measure
- Weekly: weight, waist, front and side photos.
- Every 1–2 weeks: arms (relaxed, at the widest point) and shoulders.
- Monthly: chest and thighs.
No app yet? Run the free fat vs muscle loss calculator with two body-fat readings.
FAQ
Frequently asked questions
How can I tell if I’m losing fat or muscle?
Compare your waist with your arms and shoulders over a few weeks. If your waist drops much faster, it’s mostly fat. ProgressLens does this automatically and adds what it sees in your photos.
Can it tell if I’m losing muscle on Ozempic, Wegovy or Mounjaro?
It gives you a muscle-loss signal. If your arms and shoulders shrink as fast as your waist while your weight drops quickly, the report flags it and suggests what to do. It’s an early warning from your photos and tape measurements, not a medical test, so talk to your clinician too.
Can a smart scale tell me if I’m losing muscle?
Bioimpedance scales estimate it, but readings swing with hydration, which changes a lot on a GLP-1. Tape measurements plus matched photos are a steadier signal for trends.
What should I do if it says I may be losing muscle?
Slow the rate of loss, strength-train at least twice a week, eat enough protein, and talk to your clinician if you’re on medication.
Are my photos private?
Yes. They stay inside the app on your phone, not in your gallery or a cloud, and there’s no account. When you tap AI Analyze, only the photos you chose for that report are sent to the AI. They’re not stored and not used to train any AI.