The evidence for the adverse effects of obesity on women's health is overwhelming and indisputable. Obesity, especially abdominal obesity, is central to the metabolic syndrome and is strongly related to polycystic ovary syndrome (PCOS) in women. Obese women are particularly susceptible to diabetes, and diabetes, in turn, puts women at dramatically increased risk of cardiovascular disease (CVD). Obesity substantially increases the risk of several major cancers in women, especially postmenopausal breast cancer and endometrial cancer. Overweight and obesity are associated with elevated mortality from all causes in both men and women, and the risk of death rises with increasing weight. Curbing the twin epidemics of obesity and diabetes calls for not only changes in diet and lifestyle at individual levels but also changes in policy, physical and social environment, and cultural norms.