A hamburger and fries can be just as addictive as cigarettes and even hard drugs, a surprising new study claims.
Scientists at the University of Wisconsin say high doses of fat and sugar in fast and processed foods act the same way as nicotine, heroin and other substances in becoming habit-forming.
"A high-fat diet alters brain biochemistry with effects similar to those in powerful opiates such as morphine," lead researcher Matthew Will told a British television documentary.
In Will's research - detailed in the documentary "Big Mac Under Attack," which airs in Britain tomorrow - he fed a group of lab rats high-fat diets and discovered that when the fat was taken away, the rodents displayed withdrawal symptoms similar to those of a drug addict denied a fix.
He also found that a steady diet of fat alters the development of the brain so much that it is almost impossible for a fast-food "junkie" to switch to a healthy diet.
The research was also reported in yesterday's Sunday Times of London.
Lawyers have launched a series of high-profile lawsuits against fast-food chains, claiming that they have misrepresented the effects of their products - and the new research is sure to add to the debate.
Although nutrition requirements vary according to height and build, general government guidelines recommend a daily intake of 2,300 calories for an adult male and 1,800 calories for an adult female. Of those, no more than 35 percent should be derived from fat and no more than 11 percent from sugars.