Obesity is a medical condition occurring when excess body weight may negatively impact health. It is related to nutrition and lifestyle factors. Obesity can be caused by consuming more calories than burned through diet, activity levels, medical issues, and genetics. Negative effects include increased risk of death, diseases like heart disease, stroke, diabetes, and mental health issues. Obesity is diagnosed through BMI and may involve blood tests. It can be prevented by eating less processed foods, more fruits and vegetables, controlling portions and being physically active. Treatment involves sustainable weight loss through lifestyle changes and may include medication or surgery for severe cases.