Chronotype Differences in Energy Intake, Cardiometabolic Risk Parameters, Cancer and Depression: A Systematic Review with Meta-analysis of Observational Studies

Chronotype is a behavioral manifestation of the internal circadian clock system. It refers to the specific activity-rest preference of an individual over a 24-hour period and can be assessed using different methodologies that classify individuals into morning or evening chronotype. In recent years, several studies have suggested a relationship between individual chronotype, eating habits, and the risk of developing obesity and other conditions. Our aim was to evaluate the association between chronotype, energy intake and health status through a meta-analytical approach. A comprehensive search of MEDLINE, Embase, Scopus, Web of Science and Cochrane Database was conducted. Observational studies that reported a measure of association between chronotype, energy intake and health indicators were considered eligible. Overall, 39 observational studies (37 cross-sectional studies, 2 prospective cohort studies) were included in the systematic review, with a total of 377,797 subjects. By comparing morning and evening subjects, pooled analyses of cross-sectional studies showed significantly (P < 0.001) higher levels of blood glucose [Mean Difference (MD) 7.82; 95% CI 3.18, 12.45], glycated hemoglobin (HbA1c) [MD 7.64; 95% CI 3.08, 12.21], LDL-cholesterol [MD 13.69; 95% CI 6.84, 20.54] and triglycerides [MD 12.62; 95% CI 0.90, 24.35] in evening subjects. Furthermore, an association between evening type and the risk of diabetes [Odds Ratio (OR) 1.30; 95% CI 1.20, 1.41], cancer [OR 1.18; 95% CI 1.08, 1.30] and depression [OR 1.86; 95% CI 1.20, 2.88] was reported. Regarding the other outcomes examined, no significant differences were observed between the groups in terms of energy intake, anthropometric parameters, blood pressure, insulin, total and HDL-cholesterol and hypertension risk. In conclusion, evening chronotype was associated with worse cardiometabolic risk profile and higher risk of diabetes, cancer, and depression. Further studies are needed to confirm these results and to better elucidate the interplay between chronotype, nutrition, and health status.