Adolescents' chronotype and its association with obesity-related outcomes: The EHDLA study.

Objective: This study aimed to assess associations between chronotype and obesity-related indicators in a sample of Spanish adolescents.

Methods: This cross-sectional study used data from The Eating Healthy and Daily Life Activities (EHDLA) Study, which included a representative sample of adolescents from Spain. A total of 820 adolescents (54.7% girls) aged 12-17 years were included in the analyses. The adolescents' chronotype was determined using the Morningness/Eveningness Scale in Children. Obesity-related indicators included body mass index, waist circumference, waist-to-height ratio, triceps and medial calf skinfolds, sum of skinfolds, and body fat percentage. Generalized linear models were used to examine the relationship between the Morningness-Eveningness score and chronotype status and the above-mentioned obesity-related indicators in adolescents. All analyses were adjusted for sex, age, socioeconomic status, sleep duration, physical activity, sedentary behaviour, adherence to the Mediterranean diet, and energy intake.

Results: The morningness chronotype was associated with higher abdominal obesity (odds ratio [OR] = 1.67, 95% confidence interval (CI) 1.12 to 2.50; p = 0.001), waist-to-height ratio (unstandardized beta coefficient [B] = 0.01, 95% CI 0.01 to 0.05; p = 0.029) and skinfold calves (B = 1.04 95% CI 0.24 to 1.94; p = 0.011), compared with the intermediate chronotype.

Conclusion: Adolescents with a morningness chronotype may be more prone to abdominal obesity than their counterparts with an intermediate chronotype. Effective intervention-related approaches can be applied to those with a morningness chronotype.