Concerns with eating were studied in 130 Japanese boys and 125 girls aged 6–18 years using the Simplified Eating Attitudes Test (s-EAT). The s-EAT scores in girls slightly increased with age. The mean scores in girls at age 10 years or older were significantly higher than in boys of the same age, suggesting that pubertal girls have more concerns with eating. On the other hand, s-EAT scores in boys that were not overweight decreased as they grew older, contributing, at least partly, to the sexual difference in eating behavior. The mean scores in overweight boys were higher than in boys that were not overweight. The score in boys correlated significantly with weight though there was no significant correlation in girls. These results suggest that, in addition to increased concerns with eating in girls, decreased concerns with age in boys is one of the causes of the sexual difference in eating behavior, especially during puberty. Eating behaviors in girls seem to be less influenced by changes in body weight than in boys.