The present study aims to obtain findings on the prevention of obesity in elementary school competitive judo players by investigating the relationship between body weight and body composition indices, such as the fat-free mass index (FFMI) and fat mass index (FMI). We included 581 fifth and sixth grade male and female judo players as our subjects and measured their height, body weight, and body fat percentage. We calculated their respective fat-free mass (kg) and fat mass (kg) from the data and then calculated each student’s FFMI and FMI by dividing their respective fat-free mass and fat mass by the square of their respective heights (m). The results indicate that FFMI significantly increased in boys with an increase in weight class for groups with a body weight of less than 60 kg. No statistically significant differences in FFMI were noted in groups with a body weight of greater than 60 kg. In contrast, we identified statistically significant differences in FMI across all weight classes. FFMI significantly increased in females with an increase in weight class for groups with a body weight of less than 50 kg. However, no statistically significant differences in FFMI were noted in groups with a body weight of greater than 50 kg. Similar to the male subjects, we identified significant differences in FMI across all weight classes in the female subjects.
In conclusion, generally a weight gain to greater than 60 kg in boys and toward 50 kg in girls among elementary school competitive judo players suggests that increases in fat-free mass reach a plateau and that fat mass could be the active agent.
