Objectives: To see if obesity, deaths from diabetes, and daily calorie intake are associated with income inequality among developed countries.
Design: Ecological study of 21 developed countries.
Countries: Countries were eligible for inclusion if they were among the top 50 countries with the highest gross national income per capita by purchasing power parity in 2002, had a population over 3 million, and had available data on income inequality and outcome measures.
Main outcome measures: Percentage of obese (body mass index >30) adult men and women, diabetes mortality rates, and calorie consumption per capita per day.
Results: Adjusting for gross national per capita income, income inequality was positively correlated with the percentage of obese men (r = 0.48, p = 0.03), the percentage of obese women (r = 0.62, p = 0.003), diabetes mortality rates per 1 million people (r = 0.46, p = 0.04), and average calories per capita per day (r = 0.50, p = 0.02). Correlations were stronger if analyses were weighted for population size. The effect of income inequality on female obesity was independent of average calorie intake.
Conclusions: Obesity, diabetes mortality, and calorie consumption were associated with income inequality in developed countries. Increased nutritional problems may be a consequence of the psychosocial impact of living in a more hierarchical society.