More equal but heavier: A longitudinal analysis of income-related obesity inequalities in an adult Swedish cohort

Using longitudinal data over a 17-year period for a Swedish cohort aged 20-68 in 1980/1981, this study analyses income-related inequalities in obesity. By using the concentration index and decomposition techniques we answer the following questions: 1) Does obesity inequality disfavour the poor? 2) What factors explain the inequality at different points in time? 3) What explains the change in inequality between years? We find that among females, inequalities in obesity favour the rich, but the inequality declines over time. Income itself is the main driving force behind obesity inequality, whereas being single (as opposed to being married or cohabiting) is an important counteracting factor. The main reason for the reduced obesity inequality over time is increased obesity prevalence, because in absolute terms obesity has increased uniformly across income groups. Because the income elasticity of obesity is the single most important contributor to the inequality, policies directed towards this factor might be the most effective for reducing obesity inequality. Our main income variable is within-individual mean of income, and we thereby focus on long-run inequality and are able to standardize for income mobility. The results show that inequality based on short-run income differs substantially from inequality based on long-run income. For males we find similar inequality trends as for women, although less pronounced. This difference between men and women should be taken into account when evaluating obesity reducing policies. (C) 2009 Elsevier Ltd. All rights reserved.