Association of nutritional knowledge and socioeconomic position with the double burden of malnutrition among urban and rural adults in Southwest Nigeria

Abstract Background Nigeria, like much of sub-Saharan Africa, faces a double burden of malnutrition in which undernutrition persists alongside rising overweight and obesity. Evidence on whether nutritional knowledge translates into better dietary practice among adults, and whether socioeconomic context modifies this relationship, remains inconsistent, particularly for paired urban and rural communities within the same state. Objective This study determined the association of nutritional knowledge and socioeconomic position with household dietary diversity and the double burden of malnutrition among adults in one urban community (Ado-Ekiti) and one rural community (Epe-Ekiti) in Ekiti State, Southwest Nigeria. Methods A comparative cross-sectional study was conducted between January and April 2025 among 350 adults aged 20 years and above (250 urban; 100 rural) selected through multistage sampling. A structured interviewer-administered questionnaire captured socioeconomic characteristics, household dietary diversity (Food and Agriculture Organization 12 food groups), seven-day food consumption frequency, and nutritional knowledge. Weight and height were measured directly and body mass index (BMI) was classified using World Health Organization criteria. Associations were examined using Pearson’s chi-square tests with Cramér’s V, and odds ratios (OR) with 95% confidence intervals (CI) for binary comparisons, at p < 0.05. Results Rural respondents had markedly lower socioeconomic position: 62.0% earned below ₦70,000 per month (≈ US$47; urban, 28.4%) and 24.0% had tertiary education (urban, 48.8%). High dietary diversity (≥ 6 food groups) was recorded in 69.2% of urban and 33.0% of rural respondents. A double burden of malnutrition was present in both settings: underweight affected 20.4% (urban) and 22.0% (rural), while combined overweight and obesity affected 18.4% and 25.0%, respectively. In the urban community, reported formal nutrition education was inversely associated with high dietary diversity (χ²(1) = 4.668, p = 0.031; OR 0.51, 95% CI 0.27–0.94), whereas belief in the preventive role of nutrition (χ²(2) = 7.526, p = 0.023; OR 2.08, 95% CI 1.20–3.60) and correct identification of a nutrition-related condition (χ²(3) = 18.667, p < 0.001; V = 0.273) were positively associated. In the rural community, perceived importance of balanced nutrition (χ²(2) = 21.836, p < 0.001; V = 0.467), the food-group item (χ²(2) = 14.130, p = 0.001; V = 0.376), and belief in disease prevention (χ²(2) = 15.823, p < 0.001; V = 0.398) were associated with dietary diversity, each in inverse or non-monotonic patterns. In adjusted logistic regression, the inverse urban education association attenuated to the null, whereas tertiary education (pooled adjusted OR 3.60, 95% CI 1.89–6.85) and urban residence (pooled adjusted OR 0.25, 95% CI 0.12–0.48) remained independently associated with high dietary diversity. Daily meal frequency was associated with BMI category in both settings (urban χ²(6) = 22.790, p < 0.001, V = 0.213; rural χ²(3) = 13.739, p = 0.003, V = 0.371). Conclusion Nutritional knowledge showed weak, inconsistent, and partly inverse associations with dietary diversity in both settings, whereas the large urban–rural gap in dietary diversity followed the socioeconomic divide. These findings suggest that knowledge alone may not translate into better eating and that interventions may need to combine food-based nutrition education with structural socioeconomic measures. Because the study was cross-sectional, causal inference is precluded.