Prevalence of Underweight Among Adults: United States, 2003-2006
by Cheryl D. Fryar, M.S.P.H., and Cynthia L. Ogden, Ph.D., Division of Health and Nutrition Examination Surveys
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Poor nutrition or underlying health conditions can result in underweight. Results from the 2003-2006 National Health and Nutrition Examination Survey (NHANES), using measured heights and weights, indicate that an estimated 1.8% of U.S. adults are underweight, as shown in Table 1. A statistically significant decrease in the prevalence of underweight between 1988-1994 and 2003-2006 was found only among persons who were aged 60 years and over. The prevalence in this age group was 2.3% in 1988-1994 and 1.2% in 2003-2006.
Surveys before 1988 did not include individuals over 74 years of age, and consequently, Table 2 contains age-adjusted prevalence estimates for adults aged 20-74 years for all survey periods back to 1960. The prevalence of persons who were underweight over the last 45 years has significantly decreased. Underweight prevalence went from an estimated 4% in the early 60s to approximately 2% in 2003-2006. This decrease in prevalence of underweight was found among all age groups.
Body mass index (BMI), expressed as weight/height2 (BMI; kg/m2) is commonly used to classify underweight (BMI less than 18.5) among adults (aged 20 years and over). NHANES used a stratified multistage probability sample of the U.S. civilian noninstitutionalized population. A household interview and a physical examination were conducted for each survey participant. During the physical examination (conducted in mobile examination centers), height and weight were measured as part of a more comprehensive set of body measurements. These measurements were taken by trained health technicians, using standardized measuring procedures and equipment. Observations for pregnant women and for persons missing a valid height or weight measurement were not included in the data analysis.
Tables
| Age (in years) | NHANES III (1988-1994) | NHANES (1999-2002) | NHANES (2003-2006) |
|---|---|---|---|
| Total1 | 2.4 | 1.9 | 1.8 |
| 20-39 | 3.0 | 2.8 | 2.6 |
| 40-59 | 1.7 | 1.1 | 1.2 |
| 60 or over | 2.3 | 1.6 | 1.2 |
1 Age adjusted by the direct method to the year 2000 U.S. Census Bureau estimates using the age groups 20-39, 40-59, and 60 years and over.
NOTE: NHANES is National Health and Nutrition Examination Survey.
| Age (in years) | NHES I (1960-1962) | NHANES I (1971-1974) | NHANES II (1976-1980) | NHANES III (1988-1994) | NHANES (1999-2002) | NHANES (2003-2006) |
|---|---|---|---|---|---|---|
| Total1 | 4.0 | 3.6 | 3.0 | 2.3 | 1.9 | 1.8 |
| 20-39 | 5.7 | 4.9 | 4.2 | 3.0 | 2.8 | 2.6 |
| 40-59 | 2.3 | 2.2 | 1.9 | 1.7 | 1.1 | 1.2 |
| 60-74 | 3.7 | 3.8 | 2.7 | 1.9 | 1.3 | 0.9 |
1 Age adjusted by the direct method to the year 2000 U.S. Census Bureau estimates using the age groups 20-39, 40-59, and 60-74 years.
NOTE: The National Health Examination Survey (NHES) I and the National Health and Nutrition Examination Survey (NHANES) I and II did not include individuals over 74 years of age, thus trend estimates are based on age 20-74 years.