Research, based on statistics from GP practices across the UK, shows 8.7 per cent of people living in the county are overweight and health bosses have said they are looking into ways of improving diets and health to combat a rise in obesity.

A study by health analysts Dr Foster Research has found the Shetlands had the highest obesity percentage (15.54 per cent), while people living in Camden, in North London, are the slimmest, with the area having a rating of 3.9 per cent.

A spokesman for Northamptonshire Teaching Primary Care Trust said: "Nationally we are seeing a rise in obesity, we are also seeing a rise of obesity locally as well. It's something that is being looked at very seriously.

"We are looking at a number of interventions that can be put in place to reduce the prevalence."

The report follows the publication of the Government's National Obesity Strategy, which states that, if obesity is not properly dealt with, the country may face a national crisis creating an annual heath bill of £50 billion. By 2010, there could be as many as 12 million obese adults in the UK.

From September, school dinners will have to meet strict nutritional guidelines before being served to pupils, in line with a new Government drive to tackle childhood obesity.

All school lunches in primary schools must comply with nutritional standards for limits on fat, sugar and salt content in every meal served in the canteen.

The chairman of the National Obesity Forum, Dr Colin Waine, said: "Traditionally, the worst problems have been the very industrial areas where there used to be a lot of heavy manual work.

"Those jobs have disappeared but eating habits have not changed so there is now a surfeit of calories."

Dr Waine added: "If we simply sit back and nag people we won't get on top of this problem. We have to design neighbourhoods to make physical activity safe and do-able, and modify the food we eat."