Can metformin cause weight loss?

Yes: For some medical weight loss programs metformin is used for weight loss has to be done under physician supervision.

Yes: One of the side-effects of taking metformin is some weight loss. It's not dramatic but an average of 2-3% of excess body weight and for some people it might be more, some less. Metformin is used primarily for diabetics or people with high blood sugar, pcos or Insulin resistance. It has some side-effects which some can't tolerate. So it's recommended to be prescribed only to ones who really need it.