Overweight and obese but not normal weight women with PCOS are at increased risk of Type 2 diabetes mellitus-a prospective, population-based cohort study. What are the respective roles of polycystic ovary syndrome , long-term weight gain and obesity for the development of prediabetes or Type 2 diabetes mellitus by age 46 years? The risk of T2DM in women with PCOS is mainly due to overweight and obesity, although these two factors have a synergistic effect on the development of T2DM.