Racial differences in the tracking of childhood BMI to adulthood

The possibility that there are racial differences in the patterns of BMI (kilograms per meter squared) change throughout life has not been examined. For example, the high prevalence of obesity among black women could result from a higher prevalence of obesity among black girls or because normal-weight black girls experience larger BMI increases in adolescence or adulthood than do their white counterparts. Therefore, we examined the tracking of childhood BMI into adulthood in a biracial (36% black) sample.

Five- to 14-year-old children (2392) were followed for (mean) 17 years. Childhood overweight was defined as BMI > or = 95th percentile, and adult obesity was defined as BMI > or = 30 kg/m(2).

The tracking of childhood BMI differed between whites and blacks. Among overweight children, 65% of white girls vs. 84% of black girls became obese adults, and predictive values among boys were 71% (whites) vs. 82% (blacks). These racial differences reflected contrasting patterns in the rate of BMI change. Although the initial BMI of black children was not higher than that of white children, BMI increases with age were larger among black girls and overweight black boys than among their white counterparts. In contrast, relatively thin (BMI < 50th percentile) white boys were more likely to become overweight adults than were their black counterparts.

These findings emphasize the black/white differences in BMI changes with age. Because of the adult health consequences of childhood-onset obesity, early prevention should be given additional emphasis.