Obesity is defined as having excessive body fat and increases the risk of diseases like heart disease, diabetes, and high blood pressure. You are considered obese if your weight is 20% or more above normal, your BMI is 30 or more, or your basal metabolic rate is high. BMI is a measure of weight in kilograms divided by the square of height in meters and is commonly used to classify obesity in adults. Obesity can be caused by factors such as genetics, family history, age, gender, environment, psychological problems like depression, medical illnesses, medications, and overeating.