Objective: To investigate trends in frequency of obese children in Japan over two decades, the frequency of obese children who grow into obese adults and predictive factors for adult obesity.
Design: Annual cross-sectional studies for 22 y (1974-1995) with a follow-up study.
Subjects: Cross-sectional: Cumulatively 13,186 obese (% of standard body weight (SBW): > or = 120%) schoolchildren including 3158 extremely obese (> or = 140% of SBW) children out of 203,088 schoolchildren (age: 6-14 y) in Izumiohtsu City, Osaka, Japan.
Follow-up: 151 initially obese children (initial age: 6-14 y and age at follow-up: 20-35 y) who lived in Izumiohtsu City.
Control: 3552 Japanese men and 4631 Japanese women (age: 20-35 y).
Measurements: Cross-sectional: height, weight, trunk circumference, skin-fold thickness, blood pressure and blood biochemicals.
Follow-up: height, weight, trunk circumference, skin-fold thickness during childhood, and body height and weight at follow-up. Adulthood obesity: > or = 120% of the average body mass indices (BMI) of the controls.
Results: Frequency of obese children increased from 5% to more than 10%, and that of extremely obese children increased from 1% to more than 2% during these 22 y. These increases were most prominent in the schoolboys aged 9-11 y. Prevalence of hyperglycemia and hyperlipidemia in the extremely obese children did not change, and that of hypertension and abnormal liver function gradually decreased during these two decades. After coming of age, 32.2% of the initially obese boys (relative risk: 5.3) and 41.0% of the initially obese girls (relative risk: 6.7) remained obese. BMI, percentage of the SBW and skin-fold thickness at the biceps during childhood were significantly larger in currently-obese girls. Positive correlations were demonstrated between these variables and percentage SBW at follow-up.
Conclusions: Childhood obesity is increasing in Japan, especially in boys aged 9-11 y. Approximately 32% of the obese boys and 41% of the obese girls grow into obese adults, and the degree of obesity is a predictive factor for adult obesity.