SUGAR is often given as the excuse for overeating and piling on the pounds, but now it appears it is not addictive after all.

Researchers have found that while people may become hooked on eating for its own sake, sweet treats that contain high levels of fat or sugar are no more addictive than those that do not.

While some people may consider themselves chocoholics, the evidence suggests it is all in the mind, with compulsive eating linked to psychological causes rather than any chemical dependency or need.

The international team, which included scientists from Edinburgh and Aberdeen universities, studied the way the brain responds to nutrients in food, including sugar, and compared the results to studies using substances known to cause addiction.

According to their research, the brain does not respond to nutrients in the same way as it does to addictive drugs, such as heroin or cocaine, and does not develop chemical-based cravings or any physical compulsion for extra doses.

Instead, people can develop a psychological compulsion to eat, driven by the positive feelings that the brain associates with eating.

But the scientists said this was a behavioural disorder and could be categorised alongside conditions such as gambling addiction rather than a dependency.

While it is known that fructose, a sugar found in foods ranging from biscuits to fizzy drinks, can block the chemical in the brain that controls appetite, the study is the first to show there is nothing inherently addictive about the food people like to eat.

Dr John Menzies, research fellow in the Edinburgh University's Centre For Integrative Physiology, said: "People try to find rational explanations for being over-weight and it is easy to blame food.

"Certain individuals do have an addictive-like relationship with particular foods and they can over-eat despite knowing the risks to their health.

"More avenues for treatment may open up if we think about this condition as a behavioural addiction rather than a substance-based addiction."

The research is likely to have an impact on health studies in Scotland, where nutritionists have long warned of rising levels of obesity.

The Edinburgh team said its research showed the focus on tackling the problems associated with overeating should be moved from food itself towards the individual's relationship with eating.

Professor Suzanne Dickson, of Gothenburg University and co-ordinator of the NeuroFast project, added: "There has been a major debate over whether sugar is addictive.

"There is very little evidence to support the idea any ingredient, food item, additive or combination of ingredients has addictive properties."

She added the current classification of mental disorders should now be redrawn to include a formal diagnosis of eating addiction, although more research would be needed to define a diagnosis.

As well as in Aberdeen, Edinburgh and Gothenburg, the work was carried at the Essen and Utrecht universities, in Germany and Holland, and Santiago de Compostela, Spain.

The researchers are involved in the NeuroFast consortium, which is an European Union-funded project studying the neurobiology of eating behaviour, addiction and stress.

The study, which examined the scientific evidence for food addiction as a substance-based addiction, is published in Neuroscience & Biobehavioral Reviews.