Diet diversity

In the study, diet diversity was analysed as an independent and as a moderating variable. Diet diversity was measured with Vadiveloo et al.’s (2014) US HFD^(21,24). This index captures dietary variety (number of foods), quality (concordance with the 2010 DGA) and proportionality (distribution of food groups in the diet). The index ranges between 0 (a diet with a single food) and nearly 1 (a diet with many types of food). To generate the US HFD, Vadiveloo et al. used the following equation:

where s _i is the share or proportion of each individual food or food group i based on the volume of the total diet.

where hf _i are ‘health factors’, or weights, developed by Vadiveloo et al. for each food group using qualitative and quantitative recommendations for daily food group intakes based on the 2000-kcal US Department of Agriculture Food Pattern in the 2010 DGA (See Vadiveloo et al., 2014, Table ​Table1,1, p.1565⁽²¹⁾). Health values were obtained by multiplying the reported share by the volume of each food by its respective health factors and summing them to capture diet quality and proportionality. The methodology to build the US HFD is detailed elsewhere⁽²¹⁾.

Because the focus of the study is on a lack of diet diversity, we reversed the obtained diet diversity score (1-US HFD) so that a higher score indicates less diet diversity.