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

Aims 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. Methods 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. Results Mean BMI was 28.4 ± 4.8 kg/m 2 . 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/m 2 [coefficient   =   −0.365, 95% confidence intervals ( CI ): −0.877, −0.066), whereas the direct relationship between BMI and morningness–eveningness was non‐significant. Conclusions 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.