500 mg reduces insulin resistance
which ultimately helps in Reducing the androgen levels in body.these androgen hormones are responsible for many of symptoms of PCOS
METFORMIN also Helps in regularizing your periods and helps n induction of ovulation.
However METFORMIN doesn't reduce your weight.
For reduction of weight you have to go for less calorie diet along with increased and regular exercises.
Also get your thyroid function tests
don't loose heart.be patient and you shall be able to loose weight.
You may even consult a dietician for reduction of weight.
Mind it,reduction of weight and regular exercises ate must for your regularizing of periods.