Definition & Facts for Adult Overweight & Obesity

In this section:

What are overweight and obesity?

The terms “overweight” and “obesity” refer to body weight that is greater than what is considered normal or healthy for a certain height. Overweight is generally due to extra body fat. However, overweight may also be due to extra muscle, bone, or water. People who have obesity usually have too much body fat.

Your body mass index (BMI) is one way to tell if you are at a healthy weight, overweight, or have obesity. The BMI is a measure based on your weight in relation to your height. The greater your BMI, the greater your risk of health problems from overweight and obesity.

Reaching and staying at a healthy weight may be a long-term challenge if you are overweight or have obesity. Maintaining a healthy weight—or at least not gaining more weight if you are already overweight—can help lower your chance of developing certain health problems.

Overweight family walking together outdoors.
More than 1 in 3 U.S. adults are considered to have obesity.

How common is overweight and obesity?

According to a national U.S. survey1,2,3

  • more than 1 in 3 adults were considered to be overweight
  • more than 1 in 3 adults were considered to have obesity
  • more than 2 in 3 adults were considered to be overweight or have obesity

For more statistics on overweight and obesity in the United States, see NIDDK’s Overweight & Obesity Statistics.

Who is more likely to be overweight?

Men are more likely than women to be overweight.3

Who is more likely to have obesity?

According to a national U.S. survey, some groups are more likely to have obesity.2

  • Among black adults, 48 out of 100 were considered to have obesity.
  • Among Hispanic adults, 42 out of 100 were considered to have obesity.
  • Among white adults, 36 out of 100 were considered to have obesity.

Women are more likely than men to have obesity.2

Many factors play a role in who is more likely to have obesity, and these factors may affect people differently.

Why do people gain weight?

Many factors may cause weight gain and affect how much weight your body stores. When you take in more calories from food or beverages than you use up from physical activity and through daily living, such as sitting or sleeping, your body stores the extra calories. Over time, if you continue to consume more calories than you burn off, you will likely gain weight. Excessive weight gain may lead to overweight or obesity.

Who should lose weight?

Medical experts recommend that people who have obesity should lose weight.

Most people who are overweight and have one or more factors that raise their chance for heart disease should lose weight. These factors include


Last Reviewed February 2018
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Jamy D. Ard, Wake Forest Baptist Health, Wake Forest School of Medicine