Obesity is diagnosed when a person's body mass index (BMI) is 30 or more. It occurs when the calories consumed exceed what the body needs and are stored as fat. Factors that contribute to obesity include inactivity, genetics, medical conditions, and lifestyle habits. Obesity increases the risk of many health problems like heart disease, diabetes, high blood pressure, and certain cancers. Treatment focuses on losing weight through dietary changes, increased physical activity, behavior modification, medication, and sometimes weight-loss surgery.