Losing weight costs muscle unless you spend effort keeping it. The lean-mass score is a weekly read on how much of that effort you are actually putting in, built from three things you already log.
It is a measure of your habits, not of your body. It cannot see your muscle. It can see whether you are eating enough protein and lifting often enough for the muscle you have to have a reason to stay.
Protocols are a Loopa Premium feature.
Why it exists
Roughly a quarter of the weight lost on a GLP-1 medication is lean mass (Look et al., 2025). Resistance training and adequate protein are the two things with evidence behind them for holding on to it, and both are things you do rather than things that happen to you.
So the score asks about those two, plus which way your own numbers are heading.
The three inputs
Protein, 45%. How many of the last 14 days you hit your protein goal on. Your goal comes from your weight and your protocol; see Closing the protein gap.
Resistance training, 35%. Completed strength sessions against a target of three a week (ACSM position stand, Donnelly 2009). Three or more is full marks; the count is what matters, not what was in them.
Direction, 20%. Which way your lean-mass estimate has moved over the last four weeks, from the body-fat readings you already have, whether logged, estimated from your measurements, or from a DEXA scan. Level or rising is full marks. A fall of 2% or more scores zero on this input alone.
Before it will show you a number
Two weeks of both food and training data. The later of your first meal log and your first completed session has to be at least 14 days back.
Under that, the screen says what it is waiting for rather than showing a low number. A score built on four days is a number about four days.
If you have no weight on file there is no protein goal, and so no score. Not a zero, and not a low number. Set your weight and it starts.
The third input often says N/A
Until you have two body-fat readings there is nothing to take a direction from. When that happens the 20% is shared out across the other two inputs, and the screen says the score was computed from two inputs rather than three.
It is never padded with a guess.
Reading it
- It moves weekly. Finished weeks are kept; this week is recalculated as you log.
- A low score is a list, not a verdict. The breakdown shows which input is dragging, and that is the useful part.
- It is not a comparison. Nobody else's score is visible and there is no ranking.
Raising it
- Hit protein more days. The solver on the protein screen suggests foods from what you already eat.
- Get to three sessions. Short counts. See Micro-workouts.
- Add a second body-fat reading so the third input switches on.
Related
- Protecting muscle while losing weight
- Closing the protein gap
- Micro-workouts
- BMI and body composition
- DEXA scans and body composition
- Logging a workout
Where this comes from
The lean-mass share of weight lost on GLP-1 therapy is from Look et al. (2025); the three-sessions-a-week resistance target is the ACSM position stand (Donnelly et al., 2009). Full citations are at loopahealth.app/sources. Loopa does not give medical advice, and this score is a description of your own logging rather than an assessment of your health.
