I've heard John Meadows and Dr serano discuss this a few times. I've always interpreted what they have said to be that it changes the microbiome of the gut and is not an immediate thing, but improves insulin sensitivity over time, and that alot of bodybuilders take 500mg am and pm to maintain their insulin sensitivity during GH use. Aside from that I've heard so many back and forth opinions that it's confusing. Palumbo says it's not good because it lowers igf..... Some people say take metformin during refeeds, some say take with post workout meal as a safer insulin alternative or before a keto diet to drop you into keto faster... I have a tendency to trust John Meadows opinion, because otherwise my head starts to spin everytime someone else brings up metformin and bodybuilding.