This study examined changes in body mass index (BMI), fasting blood sugar (FBS), total cholesterol (TC) and HDL-cholesterol (HDL-C) levels over a 24-year follow-up period in a pediatric cohort. An appropriate starting age for intervention to prevent cardiovascular diseases is still unclear. The subjects were 655 children, aged 10-12. A follow-up survey was conducted when the subjects reached ages 13-15, 16-18, and 35-45, respectively, and height, weight, and blood tests including FBS, TC and HDL-C were examined. Forty (6%) of these subjects participated. BMI at ages 35-45 were significantly higher than those at ages 10-12 (p < 0.0001), 13-15 (p < 0.001), and 16-18 (p < 0.001). TC levels at ages 35-45 were significantly higher than at ages 10-12 (p < 0.0001), 13-15 (p < 0.0001), and 16-18 (p < 0.0001). BMI at the end of the follow-up (ages 35-45) had a significant correlation with BMI at ages 13-15 (R = 0.38, p = 0.041) and 16-18 (R = 0.41, p = 0.049). TC and HDL-C values at the end of the follow-up had a significant correlation with those at ages 10-12 (R = 0.55, p = 0.0004; R = 0.55, p = 0.016), 13-15 (R = 0.35, p = 0.045; R = 0.42, p = 0.015), and 16-18 (R = 0.47, p = 0.019; R = 0.44, p = 0.028). These results may suggest that intervention for children in Japan with cardiovascular risk factors should be initiated in the early years of life.