The relationship among breakfast time, morningness-eveningness preference and body mass index in Type 2 diabetes

Obesity is prevalent and related to poor outcomes in Type 2 diabetes. Evening preference and late meal times have been shown to be associated with obesity, but data are lacking in people with Type 2 diabetes. This study examined the relationship among meal timing, morningness-eveningness preference and BMI in Type 2 diabetes, using a mediation analysis.

Some 210 non-shift workers with Type 2 diabetes participated in the study. Morningness-eveningness preference was assessed using a standard questionnaire, the Composite Scale of Morningness (CSM). Meal timing and daily calorie intake were obtained from 1-day food recall. A mediation analysis adjusting for relevant covariables was performed to explore whether morningness-eveningness had a direct effect on BMI, or whether the effect was mediated through the intermediate variable of meal timing.

Mean BMI was 28.4 ± 4.8 kg/m² . A higher BMI was associated with greater evening preference (P = 0.019), and non-significantly associated with late breakfast time (P = 0.053). BMI was not associated with other mealtimes or calorie intake. In addition, evening preference was associated with late breakfast time (P < 0.001). Mediation analysis revealed that breakfast time mediated the association between morningness-eveningness and BMI, i.e. morning preference (CSM ≥ 45) was associated with earlier breakfast time, and lower BMI by 0.37 kg/m² [coefficient = -0.365, 95% confidence intervals (CI): -0.877, -0.066), whereas the direct relationship between BMI and morningness-eveningness was non-significant.

Late breakfast time mediated the relationship between morningness-eveningness preference and BMI. These results suggest that circadian preference and meal timing are novel and possibly modifiable risk factors for obesity in Type 2 diabetes.