Tendency to overeat predicts an elevated body mass index trajectory across school-age years.

Overeating is a complex appetite trait, cross-sectionally linked to an elevated weight in children. However, little is known about longitudinal associations. Therefore, we studied how a tendency towards overeating predicts weight development between 8 and 16 years of age. In this study among 4517 children from the Finnish Health in Teens cohort, parents reported their child's tendency to overeat when children were on average 11.2 (SD 0.8) years old. Children were then categorised as overeating, possibly overeating, or not overeating. Height and weight measurements from two data collection periods were combined with growth data from a national health register, and age- and sex-standardised body mass index z-scores (BMIz) were calculated using the International Obesity Task Force reference. Children also reported their lifestyle factors, including food consumption, physical activity, screen time, and sleep patterns. We examined the association between overeating and BMIz using a linear mixed model, adjusting for age, sex, specific food consumption frequencies, physical activity, screen time, and sleep duration. We further analysed whether associations differed by age, food consumption frequencies, or physical activity. The average BMIz in the overeating group was 1.18 (95% CI 1.10─1.26) units higher compared with those without overeating, but remained stable as age increased. Among those without overeating, BMIz increased 0.043 units per year of age (p < 0.001). Physical activity, but not food consumption, modified the association between overeating and BMIz (p for interaction = 0.038). In the lowest third of physical activity (≤ 5 h/week), BMIz was 1.28 units higher (95% CI 1.15─1.41) in the overeating compared with the no overeating group, while in the highest third (≥ 9 h/week) the effect size was 1.08 (95% CI 0.93─1.24). In conclusion, children with a parent-reported tendency to overeat exhibited an elevated, but stable mean BMIz across adolescence. Public health programmes tackling the obesity epidemic should consider the differences in appetite self-regulation among children.