Obesity is a medical condition defined by excess body fat that may negatively impact health. A person is considered obese when their body mass index (BMI), a ratio of weight to height, exceeds 30 kg/m2. Potential causes of increasing obesity rates include lack of sleep, environmental pollutants, decreased smoking, and genetic factors passed between generations. Consequences of obesity include increased risk of heart disease, diabetes, and other health issues due to the body's inability to cope with large fat accumulation. Treatment focuses on lifestyle changes like diet and exercise, but may also include weight loss drugs or surgery for severe cases.