Objective: Many developing countries are undergoing a nutrition transition with rising rates of overweight and obesity. This nutrition transition coincides with a rapid expansion of supermarkets. The objective of the present research is to study whether supermarkets directly contribute to overweight and other changes in nutritional status.
Design: This research builds on cross-sectional observational data. Household- and individual-level data were collected in Kenya using a quasi-experimental survey design. Instrumental variable regressions were employed to analyse the impact of supermarket purchase on nutritional status. Causal chain models were estimated to examine pathways through which supermarkets affect nutrition.
Setting: Small towns in Central Province of Kenya with and without supermarkets.
Subjects: A total of 615 adults and 216 children and adolescents.
Results: Controlling for other factors, buying in a supermarket is associated with a significantly higher BMI (P=0·018) and a higher probability of overweight (P=0·057) among adults. This effect is not observed for children and adolescents. Instead, buying in a supermarket seems to reduce child undernutrition measured by height-for-age Z-score (P=0·017). Impacts of supermarkets depend on many factors including people's initial nutritional status. For both adults and children, the nutrition effects occur through higher food energy consumption and changes in dietary composition.
Conclusions: Supermarkets and their food sales strategies contribute to changing food consumption habits and nutritional outcomes. Yet the types of outcomes differ by age cohort and initial nutritional status. Simple conclusions on whether supermarkets are good or bad for nutrition and public health are not justified.
Keywords: Nutrition; Obesity; Stunting; Supermarkets.