While you make some valid points, I don’t agree with you fully. Even if a lot less than 10% of people do resistance training, that’s still a massive number. We’re talking about one of the most used diabetic drug in the last several decades. Millions of people have used it for long. A small but significant portion are interested enough in resistance training and gaining muscle that they try different exercise programs and things and monitor their effects on muscle gain and fat loss. The biggest problem I see with looking at past experience is not the number of people that have used it while doing resistance training (the number is large enough) it’s more the fact that very few of the people that have historically used metformin are healthy. Most of them of course were diabetic and there is a chance that the effect in healthy humans is not the same. But even so, its use has been popular in the longevity society for several years now and we’re not seeing any significant number of anecdotes about it effecting muscle mass gains. That doesn’t mean it can’t, just that the effect is at best relatively small.
True, but it’s not like changing your protein intake from moderate to high takes you from gaining nothing to making roid gains either. Yet bodybuilders found out long ago that higher protein helps with gaining muscles even though the difference isn’t obvious on an n=1 basis. Most of what is known about what helps and hinders muscle gains in humans has been found out by experience long before any studies found out about it because it’s easily observable and measurable by individuals.
True, but if you combine the experience of lots of people, patterns will start to be noticed. That’s how most of the things that influence muscle gain were discovered long before any studies were performed.
That is only true if the effect of metformin is very small. If you care so much about gaining maximum amount of muscles that you won’t take the chance of something that might possibly reduce muscle gain to a degree that you won’t notice, then sure, metformin is not for you. The important point is that, even if it were to have a small effect on muscle gain, that effect is insignificant relative to the effect of doing a well designed resistance training program. If muscle gains is your concern, the potential effect of metformin on it is one of the last things you should be thinking about.
AFAIK that’s not entirely true. Yes there are some studies showing that it reduced the adaption to endurance exercise in humans, but I don’t think there is any good evidence that it impairs muscle gains. Note that I asked Nir Barzilai in an online conference about the results of the TAME trial. I asked him specifically if they were monitoring effects on muscle mass. If i recall, he said that in one of the studies (I can’t remember which one) metformin was found to have a small effect on muscle mass, that is, it was reducing muscle gains slightly, but as he said, more importantly, it did not reduce muscle strength, and actually improved muscle quality!
I will say though that it’s been two years since I looked into metformin in much detail so I’m not really up to date on the newest studies. If you know about a study that showed reduced strength with metformin, please post it. Btw, personally I haven’t noticed any difference in my ability to gain muscle or strength after I started metformin many years ago (I’ve been lifting weights for 25 years). Of course that doesn’t mean it couldn’t be having a small unnoticeable effect. But if it did, why should I care, when I can easily gain muscles anyways by simply increasing my calorie intake while continuing the resistance training I’ve been doing for decades? If I was old and frail and for some reason could not do resistance training, then maybe I would care about potential tiny effects.