Longitudinal associations of eating speed and chewing frequency with anthropometric trajectories in Japanese elementary-school children: The Kuroishi oral health study

Eating speed and chewing frequency may be associated with body size; however, longitudinal evidence of their associations with anthropometric trajectories is limited. We examined the associations of chewing-related behaviours assessed in the third grade with anthropometric trajectories and incident overweight among Japanese elementary-school children. Children participating in the Kuroishi Oral Health Study who were not overweight at baseline and had at least one follow-up measurement were included in the analysis ( n = 412; 54.9% girls). Eating speed, chewing frequency, and difficulty eating hard foods were assessed using a questionnaire completed by the guardians. Body mass index (BMI), height, and body weight from the third to sixth grades were derived from school health records and analysed using linear mixed-effects models. Cox proportional hazards models were used to examine incident overweight. Fast eating and infrequent chewing were associated with higher BMI and body-weight trajectories; however, neither was associated with height trajectories. Difficulty eating hard foods was not significantly associated with anthropometric trajectories. In the combined chewing-habit analysis, children with both fast eating speed and infrequent chewing showed the highest BMI and body-weight trajectories, with differences emerging earlier than in the other groups. Fast eating and infrequent chewing were associated with incident overweight before adjustment for baseline BMI; however, the associations were not significant after adjustment. Eating speed and chewing frequency may represent behavioural markers of an emerging higher-BMI trajectory during childhood. These findings underscore the importance of considering everyday chewing habits as behavioural factors associated with weight-related growth patterns in children.