The junk food junkies

A burger, fries and a soft drink may be as addictive as heroin or tobacco, it was claimed today

The research could help explain the Western world's double epidemic of diabetes and obesity and the success of fast-food outlets.

According to John Hoebel, a psychologist at Princeton University, and Anne Kelley, a neuroscientist at the University of Wisconsin Medical School, the body can develop a craving for fat and sugar that then have to be consumed in increasing quantities to produce the same level of satisfaction. The body will also produce withdrawal symptoms when intake stops.

They say that sugar and fat stimulate the release of chemicals in the brain that behave like heroin to produce a "hit" of pleasure. Hoebel showed that rats fed a diet containing 25 per cent sugar became deeply anxious when the sugar was removed, with symptoms similar to those caused by withdrawal from heroin or nicotine. "The brain is getting addicted to its own opioids," Hoebel told New Scientist magazine. "Drugs give a bigger effect but it's essentially the same process."

Kelley found that if rats' brains were stimulated with a synthetic opioid, they ate up to six times their normal intake of fat, and raised consumption of sweet, salty and alcohol-containing solutions.

Overindulging in tasty food led to long-lasting changes in their brain chemistry similar to those caused by extended use of heroin.

But other scientists say that the evidence is not yet convincing.