Convergent validity and invariance analysis of a scale to measure adherence to eating practices recommended by the Dietary Guidelines for the Brazilian Population

Abstract

Objective: To analyze the convergent validity and invariance of a scale to measure adherence to eating practices recommended by the Dietary Guidelines for the Brazilian Population. Methods: A subsample (n=1309) of the NutriNet-Brasil cohort (self-filled web-based study) answered the 24-items scale based on the Guide, as well as socioeconomic and dietary questionnaires. The score in the scale (eGuia) was compared by Spearman’s correlation with scores of fresh and minimally processed foods (eG1) and ultra-processed foods (eG4) consumption, both composed of the average number of food items consumed in three random days. Correlations’ direction and strength were observed to infer convergent validity. A multi-group confirmatory factor analysis was used to assess scale invariance at the configural, factorial and metric levels, between subgroups of sex (men/women), age (≤37/>37, being 37 the median) and years of schooling (≤11/>11). The model was invariant when the goodness-of-fit indices varied within acceptable ranges compared to the previous level. Results: Participants were on average 39 years old (sd=13.7), 53% were women and 69% had more than 11 years of education. Correlations between eGuia and eG1, and between eGuia and eG4 were 0.56 and -0.51 (p<0.001), respectively. In all sociodemographic groups, the goodness-of-fit indices varied within acceptable ranges. Conclusion: The correlations show that the eating practices measured by the scale are aligned with a healthy food consumption, showing its convergent validity. In this sample, the scale measured the same dimensions, showed equivalence of items’ factor loadings, and generated comparable scores between subgroups of sex, age, and education.