Overeating might not be a simple matter of self-control. Lovers of burgers, fries, fizzy drinks and other fast foods could be in the grip of an addiction similar to that experienced by users of hard drugs, scientists claim.
Bingeing on foods that are high in fat and sugar may cause changes in the brain that make it hard to say no. By stimulating the brain's natural opioids, large doses of the foods can produce a high that is similar, though less intense, to that produced by heroin and cocaine, they say.
The claims are based on preliminary animal studies but are being cited by lawyers acting for overweight Americans, who in a class action against the fast food industry are seeking compensation for the cost of caring for obesity. John Banzhaf, the lawyer who took on the tobacco companies and won, is leading the case. The group includes Caesar Barber, aged 56, who has had two heart attacks and is diabetic. He claims he ate in fast food restaurants for years without being warned of the health risks.
Mr Banzhaf says that to win he only has to convince a jury that fast food companies share the blame for Mr Barber's health problems. "We might even discover that it's possible to become addicted to the all-American meal of burgers and fries," he told New Scientist.
John Hoebel, a psychologist at Princeton University, and colleagues showed that rats fed a diet containing 25 per cent sugar developed withdrawal symptoms when the sugar was removed, including chattering teeth and shivering.
When the rats were given a dose of naloxone, a drug that blocks opioid receptors, the researchers noted a drop in dopamine levels in the nucleus accumbens, a cluster of cells in the mid-brain linked with feelings of reward. Writing in Obesity Research, he says this is the same pattern of neurochemical activity seen in heroin addicts going through withdrawal. "Drugs give a bigger effect, but it's essentially the same process," he said. Other scientists, including Ann Kelley, a neuroscientist at the University of Wisconsin medical school, have observed similar changes in brain chemistry.
But Michael Jacobson, director of the Centre for Science in the Public Interest, Washington, said there was little evidence to back the claims.
Jeanne Randolph, psychiatrist at the University of Toronto with an interest in obesity, said it was well known that eating fast food and sugary snacks stimulated a cycle of instant satiation followed by a plunge in blood sugar, which triggered desire for another snack.
Yesterday Professor James Griffith Edwards, editor of the scientific journal Addiction, said: "Whether a burger habit can be regarded as an addiction depends on how you define addiction. The difference [be-tween a habit and an addiction] is not a qualitative one but a quantitative one. I am quite fond of dark chocolate but it is not going to destroy my life like a heroin addiction."
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies