A lot of things, especially with sports nutrition, performance aimed special diets, training programs, etc. relies virtually entirely on some subjective anecdotes. If they based it on objective measures and honestly represented it, they would go out of business. We are still trying to spin turk and ecdy for goodness sakes. When we have solid human data, we should use that. It’s when there’s a lack of that for which we will be reliant on trial and error + feels. Metformin we have solid human data on. If you are saying hey, getting contest ready, the metformin has a aesthetic benefit for the user, cool, go for it. Now, how about all other scenarios? Specifically around a workout. Probably not a good idea because the aesthetics don’t mean that much. If you’re on a bulk, leaving gains on the table is leaving gains on the table. I’m not saying studies are king, I’m saying when you have solid data, look at it, understand it, then apply it. Again, I didn’t say don’t use metformin. What I said is that it’s likely not a good idea to take around a workout as you are lowering the anabolic signaling. This data is very clear.
Just to give you an idea, the human study used healthy participants (granted, older men) with a placebo group and a metformin group. Both groups used a progressive resistance training program (meaning, progressive overload, this obviously transfers over to our own scenario). Placebo gained nearly double the amount of muscle mass vs the metformin group. There was also noted type 1 fiber loss in the metformin group. They were using 1.7 grams of metformin a day iirc. There was also less strength gain in the metformin group. The mechanism for which this happened is the down regulation of MTORC1. Think about this, we are constantly trying to do things to increase mTOR activity, so how does it make sense to use something that will directly inhibit that?