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Comment by arjie | Hacker News Reader

Interesting. Part of the reason I was eager to use retatrutide was the reversibility. Fantastic drug and entirely reversible. I self-tested and the effects I had on it were reversed entirely in its absence. Similar to caffeine or amphetamine at the doses I have tried (which are not high), removing the intervention resulted in a return to a prior state over a fairly short period. I'd say that, in general, some of the good properties essential to an intervention for a non-debilitating condition are:

* uniform dose-response: easy to increase effect by changing dose

* reversibility: automatic reversion to pre-intervention in a short-term is gold standard - allows for regret escape

* low-cost

GLP-1 drugs have these properties which I like. I'm surprised to hear that someone would prefer the alternative, but I must imagine that cost and the dosing structure (sub-q injection is annoying) must dominate decision making here.

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The side effect of drastic muscle loss isn't quickly reversible though.

Because muscle is about 3x as expensive to maintain as fat, unless you are on some major strength training to maintain, muscle is the very first thing that your body gets rid of when losing weight.

So now you are off the GLP-1. But you also have to eat fewer calories to maintain a calorie deficit because you no longer have all that calorie burning muscle.

* And depending on when you start your GLP-1 journey, men when they hit 40 naturally lose between 5% and 8% of their total muscle mass ++a year++ a decade (women, probably earlier). In addition to the muscle loss due to weight loss.

* And it takes approximately 3 times longer in your 50s to create a pound of muscle that it does in your 20s.

* And you can't train like you did in your 20s or you will hurt yourself.

* And as you age, your body can't absorb the protein it needs to build muscle as efficiently as it did when you are young. So you need to eat even more food to compensate.

Ok. This is now more of a rant about getting older than it is about GLP-1s.

-- Edited to reflect that muscle loss % is decade, per the corrections in replies.

If I lost 5% of my muscle mass every year since I was forty I would only have 32% of my muscle mass left. At 8% I’d be down to 16% left.

You are correct. It's per decade. Although some days it feels like I only have 16% left.

> men when they hit 40 naturally lose between 5% and 8% of their total muscle mass a year

I think your numbers might be per decade, not per year?

Oh thank God! You are correct. It's per decade.

It doesn’t have to be a foregone conclusion that GLP-1 causes muscle loss though. The primary reason for the muscle loss is the reduction in calories and protein intake. If you want to keep most of your muscle mass you can just make sure you keep up with your daily caloric and protein needs.

Muscle requires protein, yes. Unfortunately, we don't get to keep unnecessary muscle just by eating protein. The body requires a lot less muscle to lug around 200 pounds than it did when lugging around 300 pounds.

We have to do the strength training. "Use it, or lose it".

Correct, that goes without saying. I meant GLP-1 alone doesn’t cause muscle atrophy.

Are these factual claims? Seems a little fuzzy to me.

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