The primary aims of this proposal are: 1) To determine whether PCOS with liver fat >/=4.8% treated with metformin for six months will have a decline in percentage liver fat compared to a placebo group. 2) To measure the association of the PNPLA3 I148M allele with NAFLD in PCOS at baseline (n=40). 2b) To measure the association of percentage liver fat with biomarkers of NAFLD, dyslipidemia, insulin resistance and body composition at baseline (n=40) and after a placebo-controlled intervention with metformin in PCOS with liver fat >4.8% (n=20).