Actually the primary function of glucophage is it improves hyperglycemia primarily through its suppression of hepatic glucose production (hepatic gluconeogenesis); it is also an insulin sensitizer (as you noted)....but the danger for someone without diabetes/pre-diabetes and/or PCOS taking glucophage is it's action to suppress gluconeogenesis - creation of glucose in the liver, on demand, as needed to maintain blood sugar levels. When someone is doing low-carb, they depend on gluconeogenesis for blood sugar stabilization and maintaining blood sugar levels.....glucophage inhibits that action and therefore, even those with diabetes often reduce and/or stop glucophage within a few weeks of starting a low-carb diet - many find don't need it any longer.

I think taking it for weight loss is playing with fire....low-carb works well and should be the first line option sans the off-label (very questionable off-label use I'll add) use that isn't well documented.