Association between household income and overweight of Korean and American children: trends and differences

The prevalence of overweight in children has been dramatically increasing worldwide, and socioeconomic status is an important risk factor. The purpose of this study was to examine the hypothesis that household income is negatively associated with overweight in Korean and American girls and boys. In the study, 2117 children 7 to 12 years of age from the Korean National Health and Nutrition Examination Survey between 2001 and 2007 and 3016 children from the US National Health and Nutrition Examination Survey between 2001 and 2006 were included. Overweight is defined as the sex- and age-specific body mass index cutoffs recommended by the International Obesity Task Force. Lower household income significantly increased the risk for overweight in Korean boys, irrespective of adjustments. The negative association between household income and overweight of American boys disappeared after adjusting for the frequency of dining out and TV viewing time. There was no significant association between household income and overweight of Korean and American girls. As household income increased, the intake of energy from protein was increased, but energy from carbohydrates was decreased in Korean boys. On the other hand, as household income increased, energy intake from carbohydrates was increased and energy intake from proteins decreased in American boys. In conclusion, positive association between household income and overweight was found in Korean boys, but not in Korean girls and American boys and girls. Effects solely targeting reduction in income disparities cannot effectively reduce sex disparities in overweight of children.