CLUSTERS of fast food restaurants are not associated with high levels of obesity despite fears that the industry's rapid expansion has helped drive massive weight gains.

New research suggests that higher densities of fast food and full-service restaurants within a particular area are not associated with higher levels of obesity in the USA. In fact the researchers discovered that postcodes with a higher concentration of these outlets actually had lower than average rates of obesity - although this appeared to correlate with higher education and affluence.

The study was carried out by researchers from the University of Aberdeen in Scotland and the Chinese academy of Sciences.

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The researchers investigated the relationship between densities of full service and fast food restaurants and the prevalence of obesity in the United States.

The team analysed data collected in 2012 by the US Centres for Disease Prevention and Control (CDC) and compared it to data related to fast-food and full-service restaurant density as reported by the US Department of Agriculture’s Economic Research Service, but found no link between the two.

Professor John Speakman, who is based at the Institute of Biological and Environmental Sciences at the University of Aberdeen, said: “If fast food establishments have driven the obesity epidemic then one would predict that in areas where there are more of these establishments the obesity prevalence would be higher.

“However, what we actually found was that the more restaurants that there were in an area (both fast food and full service), the lower the obesity rate. This was principally because areas which tended to have the most restaurants were occupied by residents with a higher levels of education and more disposable income, which are known factors linked to lower obesity levels. When we corrected for these factors the relationship between obesity and restaurant density disappeared.”

The authors say that a potential explanation for the absence of a relationship is that on average Americans only consume about 15 per cent of their total calorie intake in restaurants.

They add: “Rising levels of obesity are leading to severe health complications and massive healthcare spending. As such, research into what is causing this worrying trend is hugely important if we are going to tackle the obesity epidemic.”

The study, published in the American Journal of Clinical Nutrition, contrasts with previous research in 2014 which found that individuals whose home or workplace was surrounded by fast food outlets - or who were exposed to large numbers of them on their route to and from work - were almost twice as likely to be obese as those least exposed to temptation.

A 2012 study also demonstrated that there were an average of 35 food outlets within a ten minute walk of secondary schools in Glasgow. However, contrary to studies based in North America and New Zealand, the study found "no clear pattern of clustering of food outlets per se or by socio-economic deprivation". They found that cafes and takeaways tended to cluster within a five minute walk of schools with fewer pupils from poorer households, and "no evidence that the major international fast food chains are located within easy reach of Glasgow school children at lunchtime".