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Comment by voldacar | Hacker News Reader

Obese people do not have enough muscle mass for 2/3 of their weight loss to be muscle

Obese people can actually be pretty muscular in my experience, due to their need to heft around their size. It's their endurance that isn't there since their hearts are quite weak.

It still won't get you to the 2/3 point making sense. If someone is 250 lbs and 35% BF and they lost 50 lbs, 2/3 of which was lean, they'd end up 200 lbs and 35.5% BF. That's possible, but I don't know if anyone would be recommending it at that point.

Peter Attia made a video recently using precisely that observation as the reason he avoids prescribing it except as a last resort, and only then when he can get patients to increase their protein intake and start strength training while getting a DEXA before and after to keep track of the relative changes in body fat percentage.

The problem is apparently that studies only use change in weight instead of body composition, so doctors have to be aware of that and get the patient measured themselves to make sure they're actually getting leaner instead of losing weight but getting "more obese".

> The problem is apparently that studies only use change in weight instead of body composition

Misinformation. Many of the studies track total fat, lean body mass, visceral fat, and literally dozens of other secondary outcomes/endpoints. See an example of such results here: https://clinicaltrials.gov/ct2/show/results/NCT03548935

This has already been covered yesterday in sibling comments about the NCT03548935 study and Peter Attia being in general a source of misinformation.

Here are some other semaglutide studies which track lean body mass specifically: https://clinicaltrials.gov/ct2/results?cond=Semaglutide&term...

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