Defining Overweight and Obesity

Overweight and Obesity Among Adults

More than one-third of U.S. adults (over 72 million people) and 17% of U.S. children are obese. During 1980-2008, obesity rates doubled for adults and tripled for children. During the past several decades, obesity rates for all population groups - regardless of age, sex, race, ethnicity, socioeconomic status, education level, or geographic region - have increased markedly.


Overweight and obesity are both labels for ranges of weight that are greater than what is generally considered healthy for a given height. The terms also identify ranges of weight that have been shown to increase the likelihood of certain diseases and other health problems.

Definitions for Adults

For adults, overweight and obesity ranges are determined by using weight and height to calculate a number called the "body mass index" (BMI). BMI is used because, for most people, it correlates with their amount of body fat.

  • An adult who has a BMI between 25 and 29.9 is considered overweight.
  • An adult who has a BMI of 30 or higher is considered obese.

It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat. For more information about BMI, visit Body Mass Index. Body Mass Index Other methods of estimating body fat and body fat distribution include measurements of skinfold thickness and waist circumference, calculation of waist-to-hip circumference ratios, and techniques such as ultrasound, computed tomography, and magnetic resonance imaging (MRI). Definitions for Children and Teens

For children and teens, BMI ranges above a normal weight have different labels (overweight and obese). Additionally, BMI ranges for children and teens are defined so that they take into account normal differences in body fat between boys and girls and differences in body fat at various ages. For more information about BMI for children and teens (also called BMI-for-age), visit BMI for Children and Teens.

Risk Factors Associated With Childhood Obesity

Health risks now

Childhood obesity can have a harmful effect on the body in a variety of ways. Obese children are more likely to have

  • High blood pressure and high cholesterol, which are risk factors for cardiovascular disease (CVD). In one study, 70% of obese children had at least one CVD risk factor, and 39% had two or more.
  • Increased risk of impaired glucose tolerance, insulin resistance and type 2 diabetes.
  • Breathing problems, such as sleep apnea, and asthma.
  • Joint problems and musculoskeletal discomfort.
  • Fatty liver disease, gallstones, and gastro-esophageal reflux (i.e., heartburn).
  • Obese children and adolescents have a greater risk of social and psychological problems, such as discrimination and poor self-esteem, which can continue into adulthood.

Health risks later

Obese children are more likely to become obese adults. Adult obesity is associated with a number of serious health conditions including heart disease, diabetes, and some cancers.

If children are overweight, obesity in adulthood is likely to be more severe.


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Content source: Division of Nutrition, Physical Activity and Obesity, National Center for Chronic Disease Prevention and Health Promotion
Page last updated: April 26, 2011

Reviewed by February 3, 2014