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How to Track Body Composition on a GLP-1: A Simple Routine

The short answer

The routine that works is boring: pick one method and stay with it, standardise the conditions so you’re measuring your body rather than your breakfast, measure monthly rather than weekly, log a strength number alongside it, and judge the trend over months. Most people’s tracking fails not because they chose the wrong tool but because they changed tools, changed conditions, or measured so often that they were reading noise. This is the whole system in six steps.

Every method in this cluster has an error bar. The routine below is designed to get signal out of them anyway — without turning your progress into a daily anxiety.

  1. 1

    Pick one method and commit to it

    DEXA if you want accuracy and can absorb the cost; a tape measure and photos if you want free and reliable; an impedance scale only if you accept it's for trends. What you must not do is mix them — switching methods gives you a change that's purely an artefact of the new tool, not of your body. Same method, and for DEXA the same machine, every single time.

  2. 2

    Standardise the conditions

    Measure under identical conditions or you're measuring your hydration and your last meal. First thing in the morning, after the toilet, before eating or drinking, not straight after exercise. It matters more than people think: in one study a 500 g meal with a litre of water shifted an impedance fat-mass estimate by around 1.4 kg and a scan's fat-free mass by over a kilogram.

  3. 3

    Measure monthly, not weekly

    Short-term readings are dominated by water — around 84% of the average two-week weight change in one study was fat-free mass rather than fat. Add each method's measurement error and weekly tracking becomes noise with a number attached. Monthly is frequent enough to catch a real trend and infrequent enough to avoid reacting to nothing.

  4. 4

    Log a strength number alongside it

    Add one thing your measurements can't see: what you can lift. Reps at a given weight, or the load itself, on two or three key movements. It's the highest-frequency signal you have about muscle, it has no error bar to speak of, and it's the cross-check when a scan or scale says something alarming.

  5. 5

    Read the trend, never the reading

    Judge direction over three to six months, not the difference between this month and last. A single measurement that moves the wrong way is usually error or water; three measurements sloping the same way is information. If you like, average the last two or three readings rather than using the latest.

  6. 6

    Know what isn't yours to interpret

    Tracking tells you whether things are moving; it doesn't diagnose anything. If a result genuinely worries you, if you're losing weight faster than expected, or if you're unsure whether you should be having scans at all, that's a conversation for your healthcare provider. And keep the purpose straight — you're checking that you're holding onto muscle, not chasing a body-fat number.

Step four is the one Mira handles for you: it logs reps, load and form score every session automatically, so the strength half of your tracking happens without you writing anything down.

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Common questions

How often should I measure body composition on a GLP-1?+

Monthly is the sweet spot for most methods. Weekly measurements are dominated by water and measurement error — in one study around 84% of the average two-week weight change was fat-free mass rather than fat. DEXA scans should be further apart still, months at minimum, because repeat scans can differ by roughly 2 kg of lean mass from measurement variation alone.

What’s the best way to track progress on a GLP-1?+

Pick one method and keep everything else constant: same tool, same conditions, first thing in the morning before food or drink, monthly. Log a strength number alongside it — reps and load on a couple of movements — because that's the one signal your measurements can't capture and it has no meaningful error bar. Then judge the trend across three to six months rather than any single reading.

Why do my body-composition numbers keep jumping around?+

Because you're seeing water and measurement error, not your body changing that fast. Food and fluid alone can move an impedance reading by well over a kilogram, and short-term weight change is mostly fat-free mass — largely water and glycogen. Standardising your conditions removes some of it; measuring monthly instead of weekly removes most of the rest.

Keep reading

Body Composition on a GLP-1

The scale can’t tell you whether you’re losing fat or muscle. The four ways to measure body composition on a GLP-1 — and how much each one can be trusted.

Are Body-Fat Scales Accurate? Reading Them on a GLP-1

Impedance scales are convenient but can be off by several percent. Why they’re extra unreliable on a GLP-1, and how to use one without being misled.

Tape Measurements and Progress Photos on a GLP-1

The free way to track body change on a GLP-1 — waist measurement and consistent photos, how to do both properly, and how much error to expect.

DEXA Scans on a GLP-1

A DEXA scan is the reference method for body composition — but it has an error bar. What it measures, how often to repeat it, and its real limits.

How to Track Strength Instead of the Scale on a GLP-1

Stop letting the scale run the show on a GLP-1 — track real progress by reps, load, and form scores, and watch your strength climb instead.