London, Jan 10 (Agencies): 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.