Background: Few studies have used the same references across countries to examine the trends of over- and underweight in older children and adolescents.

Objective: Using international references, we examined the trends of overweight and underweight in young persons aged 6–18 y from 4 countries.

Design: Nationally representative data from Brazil (1975 and 1997), Russia (1992 and 1998), and the United States (1971–1974 and 1988–1994) and nationwide survey data from China (1991 and 1997) were used. To define overweight, we used the sex- and age-specific body mass index cutoffs recommended by the International Obesity Task Force. The sex- and age-specific body mass index fifth percentile from the first US National Health and Nutrition Examination Survey was used to define underweight.

Results: The prevalence of overweight increased during the study periods in Brazil (from 4.1 to 13.9), China (from 6.4 to 7.7), and the United States (from 15.4 to 25.6); underweight decreased in Brazil (from 14.8 to 8.6), China (from 14.5 to 13.1), and the United States (from 5.1 to 3.3). In Russia, overweight decreased (from 15.6 to 9.0) and underweight increased (from 6.9 to 8.1). The annual rates of increase in the prevalence of overweight were 0.5% (Brazil), 0.2% (China), −1.1% (Russia), and 0.6% (United States).

Conclusions: The burden of nutritional problems is shifting from energy imbalance deficiency to excess among older children and adolescents in Brazil and China. The variations across countries may relate to changes and differences in key environmental factors.