obesity

Introduction
Defining obesity
The obesity epidemic
Childhood obesity
Causes of obesity
Health effects of obesity
Treatment of obesity

References & Edit History Quick Facts & Related Topics

Images & Videos

Close-up of hands using a measuring tape to measure the waist circumference of an obese man wearing a white shirt and beige pants.

How was the leptin protein in mice discovered and how has it benefited diabetes and obesity treatment in humans?

How has the study of rare conditions like lipodystrophy aided understanding of the genomic factors contributing to diabetes and obesity?

At a Glance

obesity summary

Quizzes

A Yorkshire terrier dressed up as a veterinarian or doctor on a white background. (dogs)

A Visit with the Word Doctor: Medical Vocabulary Quiz

3d illustration human heart. Adult Anatomy Aorta Black Blood Vessel Cardiovascular System Coronary Artery Coronary Sinus Front View Glowing Human Artery Human Heart Human Internal Organ Medical X-ray Myocardium

Medical Terms and Pioneers Quiz

44 Questions from Britannica’s Most Popular Health and Medicine Quizzes

Related Questions

How can childhood obesity affect a child’s education and future opportunities?
How can disruptions in leptin signaling contribute to overeating?
How can insulin resistance connect obesity with type 2 diabetes?
How can long-term obesity affect brain tissue and cognitive decline?
How can obesity affect fertility in women?
How can obesity affect testosterone levels and fertility in men?
How can reducing stomach size through surgery help treat obesity?
How can screen time contribute to childhood obesity?
How can waist circumference and waist-to-hip ratio supplement BMI measurements?
How did childhood obesity rates change in the United States during the late 20th century?
How did high-fat diets during pregnancy affect offspring in animal studies?
How did the Alliance for a Healthier Generation aim to address childhood obesity?
How do age and sex affect the interpretation of BMI?
How do genetic factors contribute to obesity in some people?
How do high-calorie foods and sugary drinks contribute to obesity?
How do leptin and insulin help regulate appetite and body weight?
How do skinfold calipers estimate body fat?
How does a sedentary lifestyle increase the risk of obesity?
How does consuming more calories than the body uses lead to obesity?
How does semaglutide help treat obesity and overweight?
How is body mass index calculated?
How is maternal diet during pregnancy linked to a child’s later food preferences?
How is obesity linked to high blood pressure and heart disease?
How is obesity linked to type 2 diabetes?
What BMI level is considered severe or morbid obesity?
What are the limitations of using BMI to assess an individual’s health?
What is gastric bypass surgery used for in obesity treatment?
Which BMI level is classified as obesity in adults?
Which BMI range is classified as overweight in adults?
Which BMI range is considered healthy for adults age 20 and older?
Which factors were included in a tool designed to predict obesity risk in newborns?
Why can muscular athletes have a high BMI without having excess body fat?
Why can very-low-calorie diets require vitamin and mineral supplements?
Why do fad diets often fail to produce long-term weight loss?
Why do some experts argue that BMI alone should not determine whether obesity is treated as a disease?
Why do some medical organizations classify obesity as a disease?
Why has the worldwide rise in obesity been linked more to environmental changes than to genetic changes?
Why is BMI interpreted differently for children than for adults?
Why is BMI not a direct measure of body fat?
Why is obesity considered a chronic condition?
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Health & Medicine Conditions & Diseases Nutritional Diseases

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External Websites

The Nemours Foundation - For Parents - Overweight and Obesity
Cleveland Clinic - Obesity
Verywell Health - Obesity
Live Science - Obesity: Causes, Complications & Treatments
Mayo Clinic - Obesity

Britannica Websites

Articles from Britannica Encyclopedias for elementary and high school students.

obesity - Children's Encyclopedia (Ages 8-11)
obesity - Student Encyclopedia (Ages 11 and up)

obesity

medical disorder

Also known as: corpulence, fatness

Written and fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Nov. 12, 2026 •History

obesity, excessive accumulation of body fat, usually caused by the consumption of more calories than the body can use. The excess calories are then stored as fat, or adipose tissue. Overweight, if moderate, is not necessarily obesity, particularly in muscular or large-boned individuals. Obesity was traditionally defined as an increase in body weight that was greater than 20 percent of an individual’s ideal body weight—the weight associated with the lowest risk of death, as determined...

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