re: Metformin in non diabetic

I don't think it is gonna do you a whole lot of good if you are not insulin resistant (and yes, this may even be related to the protective mechanism against some cancers - that is a gigantic rabbit hole for sure, and very interestingly hearkens back to early to mid 20th century metabolic cancer origin theory (ie the work of Otto Warburg), which has been largely relegated to history in favor of genetic origin theories (and I use that term generically, not in the sense of strict heritability, but rather genetic mutations). There are plenty of folks out there that are not diabetic and not overweight, are not sedentary and still have some degree of insulin resistance or are perhaps on the edges of metabolic syndrome without frankly meeting the criteria. These are very likely the non-diabetic people that would see the most benefit from "recreational" (that's tongue-in-cheek) metformin use.

The reason metformin has a place in PCOS is breaking the insulin resistance chain part of the vicious cycle type of metabolic malfunction (it is a very wide-spectrum type of disorder). Sometimes it is enough to get women over the hump ovulating either alone or in combination with either clomiphene citrate or Letrazole. To clarify sometimes we use it pre-treatment for a few months, and sometimes in concert with the aforementioned drugs.

There is interest in metformin as a "longevity" drug for sure, and a good place to start gathering some decent information on the subject is to google "metformin and Peter Attia".

That's my two cents and I'll add one more thing - often times the extended release version given in split doses can help get around the often nasty GI side effects mentioned above.