Do sleep quality and caffeine consumption mediate the relationship between late chronotype and body mass index?

Aim: To determine the role of sleep quality and caffeinated beverage consumption in the effect of late chronotype on body mass index (BMI).

Materials And Methods: The study consisted of a total of 661 healthy university students with a mean age of 21.4 ± 1.38 years. Within the scope of the study, The Morningness-Eveningness Questionnaire (MEQ) was used to determine the chronotypes of individuals, the Pittsburgh Sleep Quality Index (PSQI) was used to determine sleep quality, and a 24 h physical activity record was taken to determine physical activity levels. The caffeine intake of the individuals was determined using a food frequency questionnaire for the intake of caffeinated food and beverages. The role of mediators in the effect of late chronotype on BMI was evaluated via multiple mediation analysis.

Results: In this study, evening-type individuals had higher daily caffeine intake, worse sleep quality (P < 0.001), and higher BMI (P < 0.05). When the effect of mediators was taken into account, the negative relationship between the chronotype score and BMI was maintained (β = -0.109, 95% CI (-0.194, -0.021), P < 0.05). Decreased sleep quality had a mediated effect in this relationship [β = -0.208, 95% CI (-0.275, -0.119)], and caffeinated beverage consumption was found to have no mediator function (β = 0.040 95% CI (-0.050, 0.108), P > 0.05).

Conclusion: To conclude, eveningness chronotype had an effect on higher levels of caffeinated beverage consumption, lower sleep quality, and increased BMI. Chronotype, sleep quality, and caffeinated beverage consumption should be taken into account in studies examining the relationship between circadian rhythm and obesity.