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About two-thirds of adults in the United States
are overweight, and almost one-third are obese, according to data from the
National Health and Nutrition Examination Survey (NHANES) 2001 to 2004. This
fact sheet presents statistics on the prevalence of overweight and obesity
in the United States, as well as the health risks, mortality rates, and
economic costs associated with these conditions. To understand these
statistics, it is necessary to know how overweight and obesity are defined
and measured, something this publication addresses. This fact sheet also
explains why statistics from different sources may not match.
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What are overweight and obesity?
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Overweight refers to an excess of body weight
compared to set standards. The excess weight may come from muscle, bone,
fat, and/or body water. Obesity refers specifically to having an abnormally
high proportion of body fat.[1] A person can be overweight without being
obese, as in the example of a bodybuilder or other athlete who has a lot of
muscle. However, many people who are overweight are also obese.
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How are weight-related health risks determined? |
Various methods are used to determine if someone’s weight has increased
his or her health risks. Some are based on the relationship between height
and weight; others are based on measurements of body fat. The most
commonly used method today is the body mass index (BMI). BMI is an index
of weight adjusted for the height of an individual.
BMI can be used to screen for both overweight and obesity in adults. It is the measurement of choice for many obesity researchers and other health professionals, as well as the definition used in most published information on overweight and obesity. BMI is a calculation based on height and weight, and it is not gender-specific in adults. BMI does not directly measure percentage of body fat, but it is a more accurate indicator of overweight and obesity than relying on weight alone. BMI is calculated by dividing a person’s weight in kilograms by height in meters squared. The mathematical formula is “weight (kg)/height (m²).” To determine BMI using pounds and inches, multiply weight in pounds by 704.5,* divide the result by height in inches, and then divide that result by height in inches a second time. (You can also use the BMI calculator at www.nhlbisupport.com/bmi or check the chart below.) * The multiplier 704.5 is used by the National Institutes of Health (NIH). Other organizations may use a slightly different multiplier; for example, the American Dietetic Association suggests multiplying by 700. The variation in outcome (a few tenths) is insignificant.
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Body Mass Index Table |
To use the table, find the appropriate height in the left-hand column and then move across to a given weight. The number at the top of the column is the BMI at that height and weight. Pounds have been rounded off. |
 |
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| Source: Clinical Guidelines on Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, NHLBI, September 1998 |
| An expert panel convened by the National Heart, Lung, and
Blood Institute (NHLBI) in cooperation with the National Institute of
Diabetes and Digestive and Kidney Diseases (NIDDK), both part of NIH,
identified overweight as a BMI of 25 to 29.9 kg/m², and obesity as a BMI of
30 kg/m² or greater. However, overweight and obesity are not mutually
exclusive, since people who are obese are also overweight.[1] Defining
overweight as a BMI of 25 or greater is consistent with the recommendations
of the World Health Organization (WHO)[2] and most other countries. Calculating BMI is simple, quick, and inexpensive—but it does have limitations. One problem with using BMI as a measurement tool is that very muscular people may fall into the “overweight” category when they are actually healthy and fit. Another problem with using BMI is that people who have lost muscle mass, such as the elderly, may be in the “healthy weight” BMI category (BMI 18.5 to 24.9) when they actually have reduced nutritional reserves. BMI, therefore, is useful as a screening tool for individuals and as a general guideline to monitor trends in the population, but by itself is not diagnostic of an individual patient’s health status. Further assessment of patients should be performed to evaluate their weight status and associated health risks. For more information on measuring overweight and obesity, see Weight and Waist Measurement: Tools for Adults.
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Why do statistics about overweight and obesity differ? |
The definitions or measurement characteristics for
overweight and obesity have varied over time, from study to study, and from
one part of the world to another. The varied definitions affect prevalence
statistics and make it difficult to compare data from different studies.
Prevalence refers to the total number of existing cases of a disease or
condition in a given population at a given time. Some overweight- and
obesity-related prevalence rates are presented as crude or unadjusted
estimates, while others are age-adjusted estimates. Unadjusted prevalence
estimates are used to present cross-sectional data for population groups at
a given point or time period, without accounting for the effect of different
age variations among groups. For age-adjusted rates, statistical procedures
are used to remove the effect of age differences when comparing two or more
populations at one point in time, or one population at two or more points in
time. Unadjusted estimates and age-adjusted estimates will yield slightly
different values. Previous studies in the United States have used the 1959 or the 1983 Metropolitan Life Insurance tables of desirable weight-for-height as the reference for overweight.[3] More recently, many Government agencies and scientific health organizations have estimated overweight using data from a series of cross-sectional surveys called the National Health Examination Surveys (NHES) and NHANES. The National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) conducted these surveys. Each had three cycles: NHES I, II, and III spanned the period from 1960 to 1970, and NHANES I, II, and III were conducted in the 1970s, 1980s, and early 1990s. Since 1999, NHANES has become a continuous survey. Many earlier reports use a statistically derived definition of overweight from NHANES II (1976 to 1980). This definition (based on the gender-specific 85th percentile values of BMI for 20- to 29-year-olds) is a BMI greater than or equal to (>) 27.3 for women and 27.8 for men. NHANES II further defines “severe overweight” (based on 95th percentile values) as a BMI > 31.1 for men and a BMI > 32.2 for women.[4] Some studies round these numbers to a whole number, which affects the statistical prevalence. In 1995, WHO recommended a classification for three “grades” of overweight using BMI cutoff points of 25, 30, and 40.[5] WHO suggested an additional cutoff point of 35 and slightly different terminology in 1998.[2] The expert panel convened by NHLBI and NIDDK released a report in September 1998 that provided definitions for overweight and obesity similar to those used by WHO. The panel identified overweight as a BMI > 25 to less than (<) 30, and obesity as a BMI > 30. These definitions, widely used by the Federal Government and more frequently by the broader medical and scientific communities, are based on evidence that health risks increase in individuals with a BMI > 25. BMI cutoff points are a guide for definitions of overweight and obesity and are useful for comparative purposes across populations and over time; however, the health risks associated with overweight and obesity are on a continuum and do not necessarily correspond to rigid cutoff points. For example, an overweight individual with a BMI of 29 does not acquire additional health consequences associated with obesity simply by crossing the BMI threshold of > 30. However, health risks generally increase with increasing BMI.
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Prevalence Statistics Related to Overweight and Obesity* |
Overweight and obesity are found worldwide, and the
prevalence of these conditions in the United States ranks high along with
other developed nations.
Below are some frequently asked questions and answers about overweight and obesity statistics. Data are based on NHANES 2001 to 2004. Unless otherwise specified, the figures given represent age-adjusted estimates. Age-adjusted estimates are used in order to account for the age variations among the groups being compared. Population numbers are based on estimates from the U.S. Census Bureau’s Current Population Survey. Q: How many adults age 20 and older are overweight or obese (BMI > 25)? A: About two-thirds of U.S. adults are overweight or obese.[6] All adults: 133.6 million (66 percent) * The statistics presented here are based on the following definitions unless otherwise specified: healthy weight = BMI > 18.5 to < 25; overweight = BMI > 25 to < 30; obesity = BMI > 30; and extreme obesity = BMI > 40. Q: How many adults age 20 and older are obese (BMI > 30)? A: Nearly one-third of U.S. adults are obese.[6] All adults: 63.6 million (31.4 percent) Q: How many adults age 20 and older are at a healthy weight (BMI > 18.5 through 24.9)? A: Less than one-third of U.S. adults are at a healthy weight.[6] All adults: 65.4 million (32.3 percent) Q: How has the prevalence of overweight and obesity in adults changed over the years? A: The prevalence has steadily increased over the years among both genders, all ages, all racial and ethnic groups, all educational levels, and all smoking levels.[7] From 1960 to 2004, the prevalence of overweight increased from 44.8 to 66 percent in U.S. adults age 20 to 74.[6] The prevalence of obesity during this same time period more than doubled among adults age 20 to 74 from 13.3 to 32.1 percent, with most of this rise occurring since 1980.[6] Q: What is the prevalence of overweight or obesity in minorities? A: Among women, the age-adjusted prevalence of overweight or obesity (BMI > 25) in racial and ethnic minorities is higher among non-Hispanic Black and Mexican-American women than among non-Hispanic White women. Among men, there is little difference in prevalence among these three groups [6]. Sufficient data for other racial and ethnic minorities has not yet been collected. Non-Hispanic Black Women: 79.6 percent Non-Hispanic Black Men: 67 percent Studies using this definition of overweight and obesity provide ethnicity-specific data only for these three racial and ethnic groups. Studies using different BMI cutoff points derived from NHANES II data to define overweight and obesity have reported a high prevalence of overweight and obesity among Hispanics and American Indians. The prevalence of overweight and obesity in Asian Americans is lower than in the population as a whole.[1] Q: What is the prevalence of overweight and obesity in children and adolescents? A: While there is no generally accepted definition for obesity as distinct from overweight in children and adolescents, the prevalence of overweight* is increasing for children and adolescents in the United States. Approximately 17.5 percent of children (age 6 to 11) and 17 percent of adolescents (age 12 to 19) were overweight in 2001 to 2004.[6] * Overweight is defined by the sex- and age-specific 95th percentile cutoff points of the 2000 CDC growth charts. These revised growth charts incorporate smoothed BMI percentiles and are based on data from NHES II (1963 to 1965) and III (1966 to 1970), and NHANES I (1971 to 1974), II (1976 to 1980), and III (1988 to 1994). The CDC BMI growth charts specifically excluded NHANES III data for children older than 6 years.[8] Figure 1. Overweight and Obesity, by Age: United States, 1960-2004
Source: CDC/NCHS, Health, United States, 2006
Q: What is the mortality rate associated with obesity?
A: Most studies show an increase in mortality rates associated with obesity. Individuals who are obese have a 10- to 50-percent increased risk of death from all causes, compared with healthy weight individuals (BMI 18.5 to 24.9). Most of the increased risk is due to cardiovascular causes.[1] Obesity is associated with about 112,000 excess deaths per year in the U.S. population relative to healthy weight individuals.[9]
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Economic Costs Related to Overweight and Obesity |
As the prevalence of overweight and obesity has increased
in the United States, so have related health care costs—both direct and
indirect. Direct health care costs refer to preventive, diagnostic, and
treatment services such as physician visits, medications, and hospital and
nursing home care. Indirect costs are the value of wages lost by people
unable to work because of illness or disability, as well as the value of
future earnings lost by premature death. Most of the statistics presented here represent the economic cost of overweight and obesity in the United States in 1995, updated to 2001 dollars.[10] Unless otherwise noted, these statistics are adapted from Wolf and Colditz,[11] who based their data on existing epidemiological studies that defined overweight and obesity as a BMI > 29. Because the prevalence of overweight and obesity has increased since 1995, the costs today are higher than the figures given here. Q: What is the cost of overweight and obesity? A: Total Cost: $117 billion *A recent study estimated annual medical spending due to overweight and obesity (BMI >25) to be as much as $92.6 billion in 2002 dollars—9.1 percent of U.S. health expenditures.[12] Q: What is the cost of lost productivity related to overweight and obesity? A: The cost of lost productivity related to obesity among Americans age 17 to 64 is $3.9 billion. This value considers the following annual numbers (for 1994): Workdays lost: $39.3 million
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Other Statistics Related to Overweight and Obesity |
Q: How physically active is the U.S. population?
A: Only 26 percent of U.S. adults engage in vigorous leisure-time physical activity three or more times per week (defined as periods of vigorous physical activity lasting 10 minutes or more). About 59 percent of adults do no vigorous physical activity at all in their leisure time.[13] About 25 percent of young people (age 12 to 21) participate in light-to-moderate activity (e.g., walking, bicycling) nearly every day. About 50 percent regularly engage in vigorous physical activity. Approximately 25 percent report no vigorous physical activity, and 14 percent report no recent vigorous or light-to-moderate physical activity.[14] Q: What is the cost of physical inactivity? A: The direct cost of physical inactivity may be as high as $24.3 billion.[15] Q: What are the benefits of physical activity? A: In addition to helping control weight, physical activity decreases the risk of dying from coronary heart disease and reduces the risk of developing diabetes, hypertension, and colon cancer.[14]
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References |
[1] Clinical Guidelines on the Identification, Evaluation,
and Treatment of Overweight and Obesity in Adults—The Evidence Report.
National Institutes of Health, National Heart, Lung, and Blood Institute.
September 1998. Available at
www.nhlbi.nih.gov/guidelines/obesity/ob_gdlns.htm.
[2] World Health Organization. Obesity: Preventing and managing the global epidemic. Report of a World Health Organization Consultation on Obesity, Geneva, 3–5 June, 1997. World Health Organization. Geneva, 1998. [3] Flegal KM, Carroll MD, Kuczmarski RJ, Johnson CL. Overweight and obesity in the United States: Prevalence and trends, 1960–1994. International Journal of Obesity. 1998; 22:39–47. [4] Kuczmarski RJ, Flegal KM. Criteria for definition of overweight in transition: Background and recommendations for the United States. American Journal of Clinical Nutrition. 2000; 72:1074–1081. [5] Physical status: The use and interpretation of anthropometry. Report of a World Health Organization Expert Committee. World Health Organization: Geneva, 1995 (World Health Organization Technical Report Series; 854). [6] National Center for Health Statistics. Chartbook on Trends in the Health of Americans. Health, United States, 2006. Hyattsville, MD: Public Health Service. 2006. [7] Mokdad AH, Ford ES, Bowman BA, Dietz WH, Vinicor F, Bales VS, Marks JS. Prevalence of obesity, diabetes, and obesity-related health risk factors, 2001. Journal of the American Medical Association. 2003; 289(1):76–79. [8] Kuczmarski RJ, Ogden CL, Guo SS, et al. 2000 Centers for Disease Control and Prevention growth charts for the United States: Methods and development. National Center for Health Statistics. Vital Health Stat 11(246). 2002. [9] Flegal KM, Graubard BI, Williamson, DF, Gail MH. Excess deaths associated with underweight, overweight, and obesity. Journal of the American Medical Association. 2005; 293(15):1861–7. [10] Wolf AM, Manson JE, Colditz GA. The Economic Impact of Overweight, Obesity and Weight Loss. In: Eckel R, ed. Obesity: Mechanisms and Clinical Management. Lippincott, Williams and Wilkins; 2002. [11] Wolf AM, Colditz GA. Current estimates of the economic cost of obesity in the United States. Obesity Research. March 1998; 6(2):97–106. [12] Finkelstein EA, Fiebelkorn IC, Wang G. National medical spending attributable to overweight and obesity: How much, and who's paying? Health Affairs Web Exclusive. 2003; W3:219-226. Available at http://content.healthaffairs.org/cgi/content/full/hlthaff.w3.219v1/DC1. [13] Lethbridge-Çejku M, Vickerie J. Summary health statistics for U.S. adults: National Health Interview Survey, 2003. National Center for Health Statistics. Vital Health Stat 10(225). 2005. [14] U.S. Department of Health and Human Services. Physical Activity and Health: A Report of the Surgeon General. Centers for Disease Control and Prevention. 1996. [15] Colditz GA. Economic costs of obesity and inactivity. Medicine & Science in Sports & Exercise. 1999; S663–S667.
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Weight-control Information Network |
1 WIN Way Bethesda, MD 20892–3665 Phone: (202) 828–1025 Toll-free number: 1–877–946–4627 Fax: (202) 828–1028 Email: WIN@info.niddk.nih.gov Internet: www.win.niddk.nih.gov The Weight-control Information Network (WIN) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health (NIH), which is the Federal Government’s lead agency responsible for biomedical research on nutrition and obesity. Authorized by Congress (Public Law 103–43), WIN provides the general public, health professionals, the media, and Congress with up-to-date, science-based information on weight control, obesity, physical activity, and related nutritional issues. Publications produced by WIN are reviewed by both NIDDK scientists and outside experts. This fact sheet was also reviewed by David F. Williamson, Ph.D., CAPT U.S. Public Health Service, Centers for Disease Control and Prevention (CDC), Division of Diabetes Translation; Katherine Flegal, Ph.D., Senior Research Scientist, National Center for Health Statistics, CDC; and Rachel Ballard-Barbash, M.D., M.P.H., Associate Director, Applied Research Program, National Cancer Institute, NIH. This publication is not copyrighted. WIN encourages users of this fact sheet to duplicate and distribute as many copies as desired. This fact sheet is also available at www.win.niddk.nih.gov. Updated May 2007 |
