by EBSCO Medical Review Board

Obesity is a high amount of body fat. It leads to a much higher body weight than normal. Calories are burned through activity and body functions. Weight gain happens when the calories eaten are more than the calories used. If this happens often, it leads to obesity.

Obesity is a body mass index (BMI) of 30 or higher in an adult. Severe obesity is a BMI that is higher than 40. BMI is a person’s weight in kilograms divided by the square of height in meters

Children and teens are still growing. Their BMI is measured differently than adults. Their BMI levels are expressed in how they compare to other children of the same gender and age. Obesity in children is a BMI at or higher than in the 95th percentile. This means the child's BMI is higher than 95% of kids the same age and gender. Severe obesity is when it is at or higher than the 120th percentile.

Health Problems from Being Obese

Without treatment, obesity can raise the risk of serious health problems, such as:

What are the risk factors for obesity?What are the symptoms of obesity?How is obesity diagnosed?What are the treatments for obesity?Are there screening tests for obesity?How can I reduce my risk of obesity?What questions should I ask my doctor?Where can I get more information about obesity?


Heymsfield SB, Wadden TA. Mechanisms, Pathophysiology, and Management of Obesity. N Engl J Med. 2017;376(3):254-266.

Obesity in adults. EBSCO DynaMed website. Available at: Accessed May 5, 2022.

Obesity in children and adolescents. EBSCO DynaMed website. Accessed May 5, 2022.

Obesity. Merck Manual Professional Version website. Available at: Accessed May 5, 2022.

Treatment. National Heart, Lung, and Blood Institute website. Available at: Accessed May 5, 2022.

Revision Information