# Smart Scale Body Composition on GLP-1 Drugs: Fat vs Muscle Lost | This GLP Connected-scale data showed a 9.8% median weight reduction on GLP-1 drugs, 7.5% fat and 2.3% muscle, with systolic pressure down 2.5 mm Hg in 148 exposed users. Publisher: This GLP Editorial Team Canonical: https://thisglp.com/research/glp1-body-composition-smart-scale Updated: 2026-09-18 Published: 2026-09-16 [← Research](https://thisglp.com/research) Evidence # Smart Scale Body Composition on GLP-1 Drugs: Fat vs Muscle Lost Connected bioimpedance scales recorded a 9.8% median weight reduction on GLP-1 drugs, split 7.5% fat and 2.3% muscle, in people who weigh themselves for years. [This GLP Editorial Team](https://thisglp.com/about)September 20267 min readUpdated September 2026 Median weight change at 10 to 14 months: −9.8% · fat 7.5% · muscle 2.3% · The two shares sum to the total, so both are shares of body weight. · 2.3 of 9.8 is 23% of the weight lost. · What measured it · A connected bathroom scale, reading bioimpedance through the legs. · Not DXA. Everybody in both groups owned one and used it for years. **Research, not medical advice.** This GLP is independent and educational. Nothing here is a substitute for individualized care from a licensed clinician, and reading it creates no doctor–patient relationship. Talk to your own provider before starting, stopping, or changing any medication, peptide, or therapy. See our [methodology](https://thisglp.com/methodology) and [terms](https://thisglp.com/terms). ## Key takeaways - A retrospective cohort built from connected-scale data, 396 people starting a GLP-1 against matched non-users. - Median weight reduction over months 10 to 14: 9.8%, made of 7.5% fat and 2.3% muscle. - Those two figures sum to the total, so the muscle share of the weight lost works out at about a quarter. - Blood pressure fell 2.5 mm Hg systolic and 1.5 diastolic, in a smaller group of 148 exposed. - Fat and muscle were estimated by household bioimpedance, not by DXA. A study of body composition is only as good as the thing doing the composing. Here that thing is a bathroom scale that sends a small current through your legs and infers what is between them. That is a real measurement and a useful one. It is not the measurement the phrase “body composition” usually implies, and the difference matters more than the percentages do. [\[1\]](https://thisglp.com/research/glp1-body-composition-smart-scale#ref-1) ## What the numbers say Over months 10 to 14, the GLP-1 group showed a median weight reduction of 9.8% against matched non-users. The paper attributes 7.5% to fat mass and 2.3% to muscle mass. Those two add to 9.8 exactly, which tells you both are expressed as shares of body weight rather than of each tissue. Work it through and muscle accounts for roughly a quarter of everything lost — close to the range [the imaging studies keep landing in](https://thisglp.com/research/muscle-loss-on-glp1), which is at least a point in the method’s favor. Systolic blood pressure fell 2.5 mm Hg, interval 1.5 to 2.9. Diastolic fell 1.5, interval 1.2 to 1.9. Those came from 148 exposed people rather than 396. Intervals this tight are telling you about the method The headline reduction is reported as 9.8% with a 95% interval of 9.8 to 9.9. No clinical effect is known to a tenth of a percentage point. What is being estimated is a distributional quantity across a very large number of daily weigh-ins, and its precision describes the arithmetic rather than any individual’s result. ## Who is in a study made of scale data People who bought a connected scale, linked it to an app, weighed themselves regularly for years, and then answered a survey about their medications. Both groups. That is a population already engaged with measuring itself. Matching happens inside it, so it controls for differences between the people who are there and tells you nothing about the people who are not — the same structural limit as [a study whose sample defines its own conclusion](https://thisglp.com/research/do-glp1-drugs-help-hidradenitis-suppurativa), arriving by a different route. ## The prediction that may be a floor The strongest predictor of what the authors call weight-loss quality was the muscle-to-fat ratio somebody started with. People with less muscle relative to fat lost more fat and kept more muscle. Which is worth sitting with. Somebody carrying little muscle has little muscle available to lose, so a measure of how much muscle came off will look favorable for them almost by construction. Whether that is a clinical insight or an artifact of the ratio is not something this design can separate, and [what muscle loss does to strength](https://thisglp.com/research/semaglutide-muscle-mass-and-grip) is a different question again. ## What it is good for Scale data has one genuine advantage over a trial: it keeps going. Nobody schedules a DXA scan for a Tuesday in month thirteen, and daily home weights across years are a record no clinic produces. So read this as a long, noisy, densely sampled look at a self-selected group, and not as a body-composition study. It agrees roughly with better instruments on the split, which is reassuring, and it says nothing about [what comes back afterward](https://thisglp.com/research/do-you-lose-muscle-on-a-glp1). ## Frequently asked How much of the weight lost was muscle? The paper reports 7.5% fat and 2.3% muscle against a 9.8% total, so muscle is about a quarter of what came off. That figure follows from the published numbers rather than being stated. Is a bathroom scale accurate for body composition? It estimates rather than measures. Bioimpedance infers tissue from electrical resistance and shifts with hydration and time of day, so it is not comparable to a DXA scan. Why are the confidence intervals so narrow? Because the quantity being estimated is a distributional one computed across a very large number of daily weigh-ins. The precision describes the arithmetic, not any individual result. Did blood pressure improve? Systolic fell 2.5 mm Hg and diastolic 1.5 mm Hg, sustained over months 10 to 14. That part of the analysis had 148 exposed people rather than 396. ## Sources 1. \[1\] Chabassier A, et al. (2026). Real-World Body Composition and Blood Pressure Changes Following Glucagon-Like Peptide 1 Receptor Agonist Initiation: A Causal Inference Study of Connected Device Data Mayo Clinic Proceedings: Digital Health. [PMID 42746268](https://pubmed.ncbi.nlm.nih.gov/42746268/) ## Where to get it ### Best GLP-1 injections Every injectable seller we can verify, with the price each one publishes and an honest read of what the trials measured. 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