Associations among chronotype and eating habits in adolescents are affected by study shift: A cross-sectional study

We investigated the influence of chronotype on eating habits among adolescents attending schools with morning (07:00 hours-12:00 hours) or afternoon (13:00 hours-18:00 hours) shifts, hypothesizing that incompatibility of study schedules may be related to dietary choices. In this cross-sectional study, 734 adolescents (aged 14-19 years) completed an online questionnaire covering eating habits, chronotype, sleep duration, social jet lag, socioeconomic data, physical activity and anthropometric measures. Odds ratios with 95% confidence intervals were estimated using adjusted logistic regression, stratified by study shift. In the morning shift, a morning chronotype was associated with higher odds of breakfast (odds ratio: 3.47; 95% confidence interval: 1.13-10.71) compared with an evening chronotype. Both morning and intermediate chronotypes were associated with higher odds of morning snack (odds ratio: 3.52; 95% confidence interval: 1.13-10.93; and odds ratio: 2.87; 95% confidence interval: 1.18-6.99) and lower odds of fast foods (odds ratio: 0.09; 95% confidence interval: 0.02-0.49; and odds ratio: 0.19; 95% confidence interval: 0.58-0.62). In the afternoon shift, a morning chronotype was associated with higher odds of breakfast (odds ratio: 5.22; 95% confidence interval: 1.85-14.72), beans (odds ratio: 3.57; 95% confidence interval: 1.19-10.74), vegetables (odds ratio: 3.52; 95% confidence interval: 1.28-9.69) and fruits (odds ratio: 4.50; 95% confidence interval: 1.55-13.07) compared with an evening chronotype. Intermediate chronotype was associated with higher odds of breakfast (odds ratio: 3.71; 95% confidence interval: 2.03-6.77), morning snacks (odds ratio: 2.45; 95% confidence interval: 1.09-5.50), vegetables (odds ratio: 1.92; 95% confidence interval: 1.03-3.58) and fruits (odds ratio: 2.50; 95% confidence interval: 1.27-4.89), and lower odds of high-energy intake post-dinner (odds ratio: 0.43; 95% confidence interval: 0.22-0.85). Adolescents with an evening chronotype had lower odds of having breakfast. Both chronotype and study shifts influenced specific food consumption habits.