Explaining socioeconomic inequality in food consumption patterns among households with women of childbearing age in South Africa.

The changing food environment shifts peoples' eating behaviour toward unhealthy food, including ultra-processed food (UPF), leading to detrimental health outcomes like obesity. This study examines changes in socioeconomic inequalities in food consumption spending between 2005/06 and 2010/11 in South African households with women of childbearing age (15 to 49) (WCBA). Data come from the 2005/06 and 2010/11 Income and Expenditure Surveys. The distribution of spending according to the NOVA food classification system groupings (unprocessed or minimally processed foods, processed culinary ingredients, processed and UPF products) was analysed using standard methodologies. Changes in spending inequalities between 2005/06 and 2010/11 were assessed using the concentration index (C), while the factors explaining the changes in spending inequalities were identified using the Oaxaca decomposition approach. The Kakwani index (K) was used to assess progressivity. Results show that average real spending on all food categories, including UPF, increased between 2005/06 and 2010/11. Socioeconomic inequality in UPF consumption spending decreased (C = 0.498 in 2005/06 and C = 0.432 in 2010/11), and spending on processed foods (C = 0.248 in 2005/06 and C = 0.209 in 2010/11). Socioeconomic status, race, and urban residence contributed to overall socioeconomic inequality and changes in UPF consumption inequality between 2005/06 and 2010/11. Spending on all food categories was regressive in 2005/06 (K = -0.173 for UPF and -0.425 for processed foods) and 2010/11 (K = -0.192 for UPF and -0.418 for processed foods) because such spending comprises a larger share of poorer household's income than their wealthier counterparts. The government should address these contributors to inequality to mitigate the risks associated with UPF consumption, especially among less affluent households.