We are very concerned that the people seem to be using food allergies and intolerance as an excuse for weight gain

Sarah Schenker, British Nutrition Foundation

However, the foundation says that in truth, only a fraction of these actually have any sort of allergic or intolerant reaction to food types.

It has examined a series of worldwide studies conducted into food allergies.

These, it says, point to fewer than 1% of adults having a full-blown, potentially life-threatening food allergy.

Fewer than 2%, it says, have a milder food intolerance.

'Trendy thing'

Dr Sarah Schenker, a nutrition scientist for the foundation, said: "About 20% of the UK population perceive themselves to have an intolerance or allergy to food.

"It seems like the trendy thing to do now.

"We are very concerned that the people seem to be using food allergies and intolerance as an excuse for weight gain rather than cutting down on food and doing more exercise."

She said that many so-called allergy "experts" were charging patients large sums of money for tests with little or no scientific validity - and might even be giving potentially dangerous diet advice.

"If people are told to cut a lot of food out of their diet, they can lose the overall balance of the diet and that is no good."

She said that a true wheat allergy would certainly not result in weight gain - chronic diarrhoea would be more likely to be the outcome.

The chief executive of the British Allergy Foundation, Muriel Simmons, disputed the findings.

"Going by the cries for help that we get, it is far more common, " she told The Times.

The worldwide studies did suggest that food allergies and intolerances were marginally more commonplace in children.

Between 1% and 2% have an allergy, and between 5% and 8% have some form of food intolerance, said the foundation's review.