Obesity is a condition where a person has accumulated a high amount of body fat having a negative effect on their health. Obesity is a chronic condition defined by an excess amount of body fat. Obesity is best defined using Body Mass Index (BMI) which is calculated using a person’s height and weight. A BMI of 18.5-24.9 is considered normal weight, a BMI of 25-29.9 is considered overweight, and a BMI of over 30 is considered obese.