An Oxford University study suggests that people living in countries with 'free market' regimes are more likely to become obese due to the stress of being exposed to economic insecurity.

The researchers believe that the stress of living in a competitive social system without a strong welfare state could be causing people to overeat. According to the study published in the latest issue of the journal Economics and Human Biology, Americans and Britons are much more likely to be obese than Norwegians and Swedes.

Oxford researchers compared 11 affluent countries and found that those with a liberal market regime (strong market incentives and relatively weak welfare states) experienced one-third more obesity on average. Their analysis of nearly 100 surveys, carried out between 1994 and 2004, revealed that the highest prevalence of obesity reported in a single survey was in the United States where one-third of the population was classed as obese. By contrast, Norway had the lowest prevalence of obesity in a single survey at just five per cent.

The study compared 'market-liberal' countries (United States, Britain, Canada and Australia) with seven relatively affluent European countries that have systems that traditionally offer stronger social protection (Finland, France, Germany, Italy, Norway, Spain and Sweden). It concludes that economic security plays a significant role in determining levels of obesity. Countries with higher levels of job and income security were associated with lower levels of obesity.

In the past, the rise of obesity in affluent societies has frequently been attributed to the ready supply of cheap, accessible, high-energy, pre-processed food in fast food outlets and supermarkets. This cause is known by researchers as the 'fast food shock'. Oxford researchers measured the impact of fast food by using a price index, constructed by The Economist magazine*, showing the international variation in the cost of the McDonald's Big Mac hamburger. They found that the availability of fast food may not be as significant as previously thought, as they calculated it had half as much an effect on the prevalence of obesity as the effects of economic insecurity.

Lead author Professor Avner Offer, Chichele Professor of Economic History at the University of Oxford, said: 'Policies to reduce levels of obesity tend to focus on encouraging people to look after themselves but this study suggests that obesity has larger social causes. The onset and increase of large-scale obesity began during the 1980s, and coincided with the rise of market-liberalism in the English-speaking countries.

'It may be that the economic benefits of flexible and open markets come at a price to personal and public health which is rarely taken into account. Basically, our hypothesis is that market-liberal reforms have stimulated competition in both the work environment and in what we consume, and this has undermined personal stability and security.'

The Oxford research team based this study on observations in academic literature about animal behaviour. Animals, both in captivity and in the wild, have been found to increase their food intake when they are faced with uncertainty about their future food supply.

These latest findings suggest that obesity in affluent societies is a response to the stress of economic insecurity. The researchers found that the effects of economic security were considerably greater in causing obesity than other factors measured (the existence of a market-liberal regime; inequality, the price of fast food, and the passage of time).

'Obesity under affluence varies by welfare regimes: The effect of fast food, insecurity, and inequality' is by Avner Offer, Rachel Pechey and Stanley Ulijaszek.