Income inequality in wealthy countries is higher now than ever since the 1920s. This is not just a source of political discord because economic unfairness undermines health. Obesity is a case in point.
Obesity in an Economic-History Perspective
The industrial economy is often lauded as an engine of growth and prosperity. Yet, that economic growth opens up vast wealth gaps between individuals in a country and between entire countries. This phenomenon is not simply an unfortunate contrast between growth in one country, poverty in others, or between individual prosperity and individual destitution. It also has profound health implications.
Overall life expectancy is reduced in highly unequal countries, such as the US (76 years) and Brazil (73), compared to other countries at equivalent GDP levels, such as Japan (85) and Costa Rica (77), respectively. Despite the depressed life expectancy, residents of economically distressed neighborhoods can expect to live more than a decade less than those in the most affluent areas. Interestingly, rich people in unequal countries have lower life expectancy than rich people in more equal countries. There are many plausible explanations for this pattern. Unequal countries are less socially integrated and local communities provide less social support. One thinks of the mansions of the wealthy in Brazil often surrounded by favelas housing the poorest people. It is also striking that Americans live nine years less than the Japanese despite spending much more on healthcare. That money might be better spent addressing income inequality.
Obesity and related diseases, particularly diabetes and heart disease, play a major role in the connection between inequality and life expectancy. Together they comprise the metabolic syndrome that robs modern populations of more life years than any other cause and is credited with reversing a long history of increasing longevity associated with economic development (1).
Inequality and Body Weight
One might imagine that obesity is largely determined by diet and physical activity. What could it possibly have to do with income inequality? Plenty! Obesity levels of the elite are low compared to the poorest segment of the population. This issue has received a great deal of attention from health researchers.
From their time in the womb, children of poor parents are at a greater risk of accumulating fat. Their prenatal nutrition is worse. Fetal bodies adjust to undernutrition by conserving energy. It is as though they were reacting to famine conditions before they were even born. Interestingly, if mothers consume a high-fat diet, there is also an increased risk of obesity for offspring.
Children of poor families often suffer from food insecurity meaning that they sometimes skip meals thereby triggering the physiological response to famine. Economically depressed neighborhoods are food deserts. It is difficult to buy fresh fruits and vegetables. Children often subsist on snack foods. These are loaded with sugar and fats that are conducive to putting on weight and developing metabolic syndrome. We know this because experimental rodents fed on snack foods like potato chips, salami, chocolate, and ice cream rapidly develop obesity.
Poor neighborhoods are often unsafe for children to play outdoors. They spend much of their time in sedentary indoor pursuits. Dangerous environments are also psychologically stressful. Stress increases binge eating of high-energy foods like potato chips and ice cream. Greater family insecurity and exposure to police and the justice system are additional stressors in the lives of poor families.
Life in unequal societies is much more stressful, not just for the poor but even for the affluent who experience the threat of crime and random violence. People under stressful conditions often have disordered eating patterns. They are more likely to binge eat and such stress-induced eating involves high-calorie foods that promote overweight.
In countries that have higher income inequality, poor people eat out at fast-food restaurants more often (2). This could be because fast food is as cheap as cooking meals at home. Fast food restaurants serve large portions of high-fat and high-sugar foods like hamburgers and ice cream. Leading health researchers concluded that income inequality in a country causes obesity (2).
This conclusion is not strictly correct because most of the evidence is based on correlations and correlation is not the same as causation. Yet, the causal conclusion offers a reasonable summary of a mountain of evidence. If it looks like a duck, walks like a duck, and quacks like a duck, maybe it is a duck.
