Household Composition May Modify the Association Between Home Cooking and Dietary Diversity Among Japanese Corporate Employees

Background: Dietary diversity, commonly assessed using the Shannon index, reflects dietary structure and food-group variety. However, whether dietary diversity is more closely associated with demographic characteristics or lifestyle-related factors remains unclear. Objective: To examine associations between dietary diversity based on 10 food groups and demographic and lifestyle-related factors among Japanese corporate employees. Methods: This cross-sectional study analyzed data from 925 company employees aged 20–59 years. The Shannon index was calculated from 10 food groups. Associations with age, sex, body mass index (BMI), workplace location, occupation, household composition, home cooking, and lunch type were evaluated using analysis of variance, analysis of covariance (ANCOVA), and permutational multivariate analysis of variance (PERMANOVA). Results: Dietary diversity was more closely associated with lifestyle-related factors, particularly household composition and home cooking, than with demographic characteristics. Individuals living alone exhibited lower Shannon index values than those living in multiperson households. Notably, home cooking was associated with greater dietary diversity among participants in multiperson households, whereas no such association was observed among individuals living alone. PERMANOVA analyses also suggested differences in dietary structure according to household composition. Conclusions: Household composition may influence dietary structure and may modify the association between home cooking and dietary diversity. These findings suggest that determinants of dietary diversity may be context-dependent.