Text Box: INDIVIDUAL CHANGES OF BODY MASS INDEX IN JAPANESE SCHOOLBOYS Iwata F, Hara M, Okada T, Harada K Dept. of Pediatrics, Nihon University School of Medicine, Tokyo, Japan Objective: To determine the usefulness of body mass index as assessment of the changes of body fatness in individual schoolboys. Subjects: Fifty Japanese schoolboys were participated. Measurements: Height, weight, skinfold thickness (subscapular and triceps) and bioelectorical impedance were measured. We examined the three-year changes of body mass index (BMI) and weight/standard weight (W/SW) in each individual, from 9 to 12 years of age. Multiple regression analysis was used to model the relation between three-year changes of BMI, W/SW and three-year changes of body composition variables (lean body mass (LBM), skinfold thickness (ST), fat mass (FM) and fat percent (F%)). Results: The mean change of BMI was 1.7¡À0.3 (mean¡ÀSE) and that of W/SW was 2.2¡À1.9. A strong liner correlation was found for them (r=0.907, p<0.0001). In 88.0% of children BMI increased, whereas 38.0% of them showed a decrease in W/SW. Multiple regression analysis showed that the change of LBM, ST and F% had an influence on the change of BMI, while only the change of ST affected that of W/SW. Conclusion: In this study of individual changes, an increase of BMI did not always indicate a tendency toward overweight. And a change of BMI was affected by both fat and fat free mass. On the other hand that of W/SW represented the change of fatness. To assess obesity in individuals during the growing period, W/SW was suggested to be a better index. 2502