Glapp maps how the week feels.
Bild Health measures what you keep.

Glapp is an unusually likeable product and it is worth saying why first. It is built by two people who are on the medication themselves. It organises the week around six named phases of the injection cycle and asks what actually happens in them (food noise, hunger, cravings, mood, sleep, energy, bowel movements), which is a far more honest account of life on a GLP-1 than a dose checkbox. It tracks your vials and pens with remaining doses and expiry dates, which sounds mundane until the week you nearly run out. It runs on iPhone, Mac, Apple Watch, Android and the web. And it says plainly that it does not monetize your data.

It is also, by its own framing, an app about how your body feels rather than what your body is made of. That is a deliberate position, not an oversight. This page is not an argument that Glapp got it wrong. It is an argument that the readout it chose runs on a different clock from the one your muscle does.

Two clocks

Food noise, nausea, energy and mood move within hours of a shot, and you feel all of it. Scale weight moves in days, with a few pounds of water noise on top. Fat mass and lean mass move over weeks and months, and they produce no sensation at all on the way.

That is the whole problem in one sentence: the two signals that decide what you keep are the two with nothing attached to them that you can notice. The large trials did not establish the lean-mass share of weight loss by asking participants how they felt. They scanned them.

It is tempting to use the felt week as a proxy anyway: energy is fine, training is going well, so the composition must be fine too. The sleep study above is what happens to that assumption: same deficit, same two weeks, and the amount of lean tissue lost moved by roughly 60% on a variable people are notoriously bad at judging in themselves. The clinical definitions point the same way. Low muscle mass is diagnosed from measured mass and measured strength, never from how someone reports feeling. Not because symptoms don’t matter, but because they arrive late.

Feature by feature

Twelve rows: Glapp wins the cycle-phase log and supply tracking outright, leads on titration guidance, and ties six more, the Watch app among them. The gap runs the other way only at the bottom of the table, and that is the half of the year you cannot feel.

What each record is good for

The honest conclusion is not that one app is right. A GLP-1 year has a fast loop and a slow loop, and they need different instruments. The fast loop is adherence, side effects, food noise and morale, and Glapp is genuinely excellent at it. The slow loop is what the deficit is doing to your body, and it needs a measurement chain: a body-composition scale for cadence, Apple Health to carry the readings, a scan to anchor them, and charts built around two masses instead of one weight.

If you already love Glapp, what Bild Health adds is the second loop. Fat mass and lean mass in pounds, on separate lines, with every dose step dated in the same record and a protein target computed against the lean number rather than the scale number. That target has a free calculator, the plan around it is the keep-the-muscle guide, and where both apps sit among the thirteen is the full comparison.

Where these numbers come from, and what they don’t cover

The lean-mass share on this page is the span reported across a 2026 meta-analysis of 20 randomised trials measured by DEXA or MRI (a two-author review, pooling each medication’s trials separately). The sleep study is a crossover in ten people over fourteen days in a diet-induced deficit, not on any medication, and should be read as striking rather than settled. The muscle-loss review predates the GLP-1 era and speaks to weight loss generally. No randomized trial has tested sleep, protein or training in people taking a GLP-1 specifically — the evidence comes from energy-deficit studies generally, which is exactly why measuring your own result matters.