Prospective and bidirectional associations between caloric midpoint and adiposity from 7 to 10 years of age

A later daily distribution of energy intake has been inconsistently associated with adiposity in adults but studies in children are lacking. We aimed to assess the potential prospective and bidirectional associations between caloric midpoint and adiposity at ages 7 and 10 years. We selected a sample of 1910 participants of the Generation XXI birth cohort (Portugal). Using ≥2 food diaries, we computed the caloric midpoint, i.e., the clock time at which 50 % of total daily energy intake is achieved. Sex- and age-specific z-scores for body mass index (zBMI) and waist-to-height ratio (zWHtR) were obtained. We assessed the prospective association of caloric midpoint at age 7 with zBMI and zWHtR at age 10, using sex-stratified regression models adjusted for zBMI/zWHtR at 7 years, age, energy-dense foods' intake, maternal education and BMI. Bidirectionality between caloric midpoint and zBMI from ages 7 to 10 was assessed by cross-lagged panel models. After adjustments, caloric midpoint at age 7 was negatively associated with zBMI at age 10 in females (B = -0.032; 95 %CI: -0.056, -0.008). In females, there was a bidirectional negative association which was stronger from zBMI at age 7 to caloric midpoint at age 10 (stdβ2 = -0.077, P = 0.021) than from caloric midpoint at age 7 to zBMI at age 10 (stdβ1 = -0.037, P = 0.013). Associations with zBMI in males and zWHtR in either sex were weaker and not statistically significant. A weak reciprocal negative association between caloric midpoint and zBMI may exist in females aged 7 to 10; this novel finding warrants careful interpretation and further investigation. Factors driving sex-differences and bidirectional associations should be explored.