OBJECTIVE: To describe the prevalence of, and trends in, overweight and obesity in the US population using standardized international de®nitions. DESIGN: Successive cross-sectional nationally representative surveys, including the National Health Examination Survey (NHES I; 1960±62) and the National Health and Nutrition Examination Surveys (NHANES I: 1971±1974; NHANES II: 1976±1980; NHANES III: 1988±94). Body mass index (BMI: kgam 2 ) was calculated from measured weight and height. Overweight and obesity were de®ned as follows: Overweight (BMI ! 25.0); pre-obese (BMI 25.0±29.9), class I obesity (BMI 30.0±34.9), class II obesity (BMI 35.0±39.9), and class III obesity (BMI^40.0). RESULTS: For men and women aged 20±74 y, the age-adjusted prevalence of BMI 25.0±29.9 showed little or no increase over time (NHES I: 30.5%, NHANES I: 32.0%, NHANES II: 31.5% and NHANES III: 32.0%) but the prevalence of obesity (BMI^30.0) showed a large increase between NHANES II and NHANES III (NHES I: 12.8%; NHANES I, 14.1%; NHANES II, 14.5% and NHANES III, 22.5%). Trends were generally similar for all age, gender and race-ethnic groups. The crude prevalence of overweight and obesity (BMI ) 25.0) for age^20 y was 59.4% for men, 50.7% for women and 54.9% overall. The prevalence of class III obesity (BMI^40.0) exceeded 10% for non-Hispanic black women aged 40± 59 y. CONCLUSIONS: Between 1976±80 and 1988±94, the prevalence of obesity (BMI^30.0) increased markedly in the US. These ®ndings are in agreement with trends seen elsewhere in the world. Use of standardized de®nitions facilitates international comparisons.

Objective. To present a clinical version of the 2000 Centers for Disease Control and Prevention (CDC) growth charts and to compare them with the previous version, the 1977 National Center for Health Statistics (NCHS) growth charts. Methods. The 2000 CDC percentile curves were developed in 2 stages. In the first stage, the empirical percentiles were smoothed by a variety of parametric and nonparametric procedures. To obtain corresponding percentiles and z scores, we approximated the smoothed percentiles using a modified LMS estimation procedure in the second stage. The charts include of a set of curves for infants, birth to 36 months of age, and a set for children and adolescents, 2 to 20 years of age. Results. The charts represent a cross-section of children who live in the United States; breastfed infants are represented on the basis of their distribution in the US population. The 2000 CDC growth charts more closely match the national distribution of birth weights than did the 1977 NCHS growth charts, and the disjunction between weight-for-length and weight-for-stature or length-for-age and stature-for-age found in the 1977 charts has been corrected. Moreover, the 2000 CDC growth charts can be used to obtain both percentiles and z scores. Finally, body mass index-for-age charts are available for children and adolescents 2 to 20 years of age. Conclusion. The 2000 CDC growth charts are recommended for use in the United States. Pediatric clinics should make the transition from the 1977 NCHS to the 2000 CDC charts for routine monitoring of growth in infants, children, and adolescents.

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