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Comment by lores | Hacker News Reader

The drug does not directly affect muscle mass (unless you are already very lean), but heavy people are doing resistance training against their own body weight all the time, so they are strong in the absolute, even if not relatively. Weigh less and your muscles have it easier, so weaken, unless you keep them strong with exercise.

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I’m not sure that’s exactly what’s happening with GLP-1 drugs. I lost 40 pounds very quickly on them and hurt my hip then my shoulder then my wrist. Felt like I was constantly getting muscle strains and random injuries.

I started drinking a protein shake once a day and the random mysterious injuries stopped.

I'm on them too, and after being seriously grumpy for a while it dawned on me that not being hungry doesn't mean my body doesn't need satisfying food. I think it's easy to fall into 'don't need to eat, won't eat' and then get some form of malnutrition. I force myself to make good food and just eat less of it, so far it worked *fingers crossed*

A single protein shake typically provides around 22g of protein, which is a small portion of the recommended daily intake for maintaining muscle, generally close to 1g of protein per pound of body weight. As an example, I'm currently on a weight loss diet and have a 180g of proteins target per day. Unless you were significantly under-consuming protein, it's unlikely that the shake alone made a major difference.

Such high recommendations are for people that want to maximize muscle retention / growth not people that just want to be healthy. You can get by on much less.

But strength training is required anyone who wants to be healthy [0]. The RDA is just for avoiding clinical deficiency.

[0] https://www.barbellmedicine.com/blog/where-should-my-priorit...

Right but even on the low end of recommended daily protein intake, 22g would probably still be a small fraction.

The RDA is 0.37 g/pound. For a 180 pound guy, that means 67g of protein. That might sound low, but wait... At least according to this one page I found, 25% of American adults eat below RDA. It's not hard to imagine then that there are many people for whom 22g extra could make a decent difference.

0.37g/pound is on the very very low end though, far from optimal on a weight loss diet.

See this article: https://www.healthline.com/nutrition/high-protein-diet-plan#...

> The Recommended Dietary Allowance (RDA) of protein is 0.8 g per kilogram of body weight (g/kg/bw), or 0.36 g per pound of body weight (g/lbs/bw).

> However, the authors of a 2019 review suggest that this number is often misinterpreted as the ideal number. It’s only the minimum amount of protein required to prevent nutrient deficiencies and muscle loss in most healthy individuals.

> A 2017 study found that participants who ate a high protein diet of 1.34 g/kg/bw (0.6 g/lbs/bw) for more than 75% of the 6-month duration experienced significantly more weight loss than the group who followed the RDA requirements.

> A 2016 review found that eating up to 2 g/kg/bw (0.9 g/lbs/bw) may help promote strength and prevent muscle degeneration.

etc.

Kinda missing the point. For you, supplementing 22g is nothing. For something that is deficient it could be quite a difference maker.

This is likely just from losing weight rapidly in general. We see it with people losing weight from a variety of other sources, too. It's possible GLP-1s might enhance the effect in some way, but it's already a significant enough issue in general that adequate protein intake + some resistance training is important regardless.

the caloric restriction that these drugs engender can indeed lead to various forms of under-nourishment. as you point out, your protein needs (as a proportion of calorie sources) go UP when you are in caloric restriction; see PSMF.

What you described doesn’t seem to be in conflict with what he described

If the muscles had been reducing in concert with the reduced musculature needs of my body I wouldn’t be injuring myself.

I don't think that's the mechanism. A caloric deficit causes your system to metabolize whatever it can. It likes fat because that's energy dense, but muscle is also a good source of energy as well, and the more rapid the weight loss, the more body mass it has to burn.

As far as I know, muscle is only used when fat reserves are depleted or you don't eat enough protein for the brain's personal amino acid supply. I'm not particularly knowledgeable about this, though, maybe an expert can weigh in.

Not an expert, but from my own research muscle will always atrophy to its functionally base necessary mass, there are of course genetics involved in muscle mass retention as well that can’t be overlooked. But you can be in a caloric deficit and your body is burning fat(which often times this leads to lower energy and less intense resistance training) while still losing muscle mass. I don’t believe they’re mutually exclusive.

You’re 100% right though, the key to retaining muscle mass while in a caloric deficit is consuming sufficient protein, or even over-consuming protein. In starvation situations muscle is next up after fat when getting consumed for energy but it seems like for the most part the muscle mass deterioration during significant weight loss periods is a natural side effect of the process and lifestyle required to accomplish it.

>1) compared with persons with normal weight, those with obesity have more muscle mass but poor muscle quality; 2) diet-induced weight loss reduces muscle mass without adversely affecting muscle strength; 3) weight loss improves global physical function, most likely because of reduced fat mass; 4) high protein intake helps preserve lean body and muscle mass during weight loss but does not improve muscle strength and could have adverse effects on metabolic function; 5) both endurance- and resistance-type exercise help preserve muscle mass during weight loss, and resistance-type exercise also improves muscle strength. We therefore conclude that weight-loss therapy, including a hypocaloric diet with adequate (but not excessive) protein intake and increased physical activity (particularly resistance-type exercise), should be promoted to maintain muscle mass and improve muscle strength and physical function in persons with obesity.

https://pmc.ncbi.nlm.nih.gov/articles/PMC5421125/

The body needs protein to function (the body is partially built out of protein, and also proteins perform many important functions in the body), and it cannot be synthesized from fat or carbs. The body also has no store of protein. This means that outside of dietary protein, breaking down muscles is the only option.

Secondary to that, the body needs some amount of glucose. The best option for that is stored glycogen. When those stores run out the body can enter ketosis which reduces but does not eliminate the need for glucose. Fat consists of three fatty acids joined by a glycerol part. Most of the energy is in the fatty acids, but the glycerol can serve as a limited supply of glucose. However that is not really sufficient, so to get more glucose, and the other option is breaking down protein.

Any calorie deficit of 500 under BMR and the body will not just consume the fat stores but also muscle. That’s what I learned on the bodybuilding forums at least. Some people went too high on the deficit and ended up losing some muscle definition

It's more likely to happen if your deficit below TDEE is greater than 500 Calories. If you're 500 below BMR, you're almost definitionally losing weight at an unsustainably unhealthy rate, like much greater than 1% of your bodyweight lost per week.

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