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Weight and well-being: is obesity socially contagious?

How much of the rise in obesity is a result of people subconsciously "keeping up with the weight of the Joneses"? Andrew Oswald and colleagues find evidence that well-being is correlated with a person’s body mass index, and that weight perceptions are influenced by comparisons with others.

The citizens of the rich countries of the world are approximately ten kilos heavier than they were a few decades ago. Some writers argue that this dramatic rise in obesity has been generated by falling food prices. But it is not easy to see how this trigger can be large enough to match the data – and the puzzle remains of why, if fatness is a response to greater real purchasing power, we routinely observe that rich people are thinner than poor people.

Other commentators speak of an obesity "epidemic," language that is evocative of the idea that fatness can spread from one person to another. Is it possible that weight gains can spread through a population in a way reminiscent of a contagious disease?

More than one third of Europe’s population view themselves as overweight

The starting point for our exploration of this question is the idea that people care about their status and position in society. We consider the possibility that just as people’s happiness may depend on their relative income, so it may depend on their relative weight.

Personal appearance is immediately observable to others, and people have to compete for job promotions, sexual partners and much else. This means that choices about physical characteristics such as body weight may be determined – whether consciously or unconsciously – in a way that depends on other people’s choices.

Studies have suggested that it is psychologically preferable to be unemployed in areas where there are many other jobless people. This is presumably for reasons of reduced stigma. For equivalent reasons, it may be easier to be fat in a society that is fat.

We document international patterns in well-being, weight, dieting and people’s perceptions of being overweight, drawing on data from the Eurobarometer surveys, the German Socioeconomic Panel and three British data sets – the 1958 and 1970 birth cohort studies and the Health Survey of England.

Although much remains to be understood, we find evidence that comparisons and relative weight do matter – that people’s body mass index (BMI) is influenced to some degree by their relative BMI. This is consistent with the idea that there can be a ‘keeping up with the Joneses’ effect, which manifests itself as a kind of obesity imitation or contagion.

Highly educated people are the most likely to see themselves as overweight

Our study reaches a number of specific conclusions. First, we find that more than one third of Europe’s population view themselves as overweight. In the entire sample of nearly 30,000 people – roughly 1,000 randomly selected individuals in each of 29 countries – 31% of men and 43% of women say their own weight is too high. For any given BMI value, women are much more prone to feel overweight than men.

Moreover, individuals’ perceptions depend on their socio-economic characteristics. For example, highly educated people are the most likely to see themselves as overweight once BMI is held constant. This suggests that people have different comparison groups, with the highly educated holding themselves to a thinner standard.

For European women, there is evidence that weight dissatisfaction and overweight perceptions depend not just on their own BMI, but also on their BMI relative to other people. The same may be true of dieting decisions.

Data on the nature of the relationship between people’s BMI and their well-being suggest a mixed picture. In some cases, the effect is negative, confirming the presumption in much medical and psychological research that a high BMI is bad for physical and mental well-being.

But in other cases, the effect seems to be positive. This is a puzzle, suggesting the need for much more longitudinal research on the links between BMI and well-being. We are a long way from a deep causal understanding of the links between body weight and mental well-being.

But we do uncover some evidence in the German data that is consistent with comparison effects. For men in Germany, life satisfaction is greater among those who live in places where other people tend to be fatter.

All of these results should be viewed with caution. But there are some grounds to take seriously the possibility of socially contagious obesity.

Publication details

"Imitative Obesity and Relative Utility" was prepared by David Blanchflower, Andrew Oswald and Bert Van Landeghem for the NBER Summer Institute on Health Economics held in July 2008. The paper is available from: http://www2.warwick.ac.uk/fac/soc/economics/staff/faculty/oswald/ao23julyobesity08.pdf.

The authors

David Blanchflower is Bruce V. Rainer Professor of Economics at Dartmouth College and an external member of the Bank of England’s Monetary Policy Committee. Andrew Oswald is Professor of Economics at the University of Warwick. Bert Van Landeghem is at the LICOS Centre for Institutions and Economic Performance and the Department of Economics of the University of Leuven.

Further reading

  • Blanchflower, David, and Andrew Oswald. 2004.”Well-being over Time in Britain and the USA.” Journal of Public Economics 88: 1359-86.
  • Blanchflower, David, and Andrew Oswald. 2008. “Hypertension and Happiness across Nations.” Journal of Health Economics 27: 218-33.
  • Blanchflower, David, and Andrew Oswald. 2008. “Is Well-being U-shaped over the Life Cycle?" Social Science and Medicine 66: 1733-49.
  • Oswald, Andrew. 1983 “Altruism, Jealousy and the Theory of Optimal Non-linear Taxation.” Journal of Public Economics 20: 77-87.
  • Oswald, Andrew. 1997. “Happiness and Economic Performance.” Economic Journal 107: 1815-31.
  • Oswald, Andrew, and Nattavudh Powdthavee. 2007. “Obesity, Unhappiness, and the Challenge of Affluence: Theory and Evidence.” Economic Journal 117: F441- 54.
  • Oswald, Andrew, and Nattavudh Powdthavee. 2008. “Does Happiness Adapt? Longitudinal Evidence on Disability with Implications for Economists and Judges.” Journal of Public Economics 92: 1061-77.