Washington, May 22 (IANS) The reason anorexic young women don't like to eat may finally be out. Instead of igniting pleasure, food affects the part of the brain that triggers anxiety in such people.

Most people find eating to be a pleasant and rewarding experience. But people with anorexia nervosa often say eating makes them more anxious, and food refusal makes them feel better.

While most people have great difficulty in dieting and losing weight, particularly if a diet extends over many months or years, individuals with anorexia nervosa can literally diet themselves to death.

In fact, this disorder has a very high death rate from starvation. A new study sheds light on why these symptoms occur in anorexia nervosa, the International Journal of Eating Disorders reports.

Research over the past decade has provided new insights into the brain mechanisms that are associated with the rewarding aspects of eating. One of these brain chemicals is dopamine, which is released when people or animals eat tasty foods.

A study led by Walter Kaye, professor of psychiatry at the University of California, San Diego School of Medicine, used a brain imaging technology called positron emission tomography (PET), which permits visualization of dopamine function in the brain.

In order to provoke dopamine levels in the brain, scientists administered a one-time dose of the drug amphetamine, which releases dopamine in the brain, according to a California statement.

In healthy women without an eating disorder, amphetamine-induced release of dopamine was related to feelings of extreme pleasure in a part of the brain known as a "reward" centre.

However, in people who had anorexia nervosa, amphetamine made them feel anxious, and the part of the brain that was activated was, instead, one that worries about consequences.

"This is the first study to demonstrate a biological reason why individuals with anorexia nervosa have a paradoxical response to food," said Kaye.