IN TIMES of stress, foods such as apple pie, biscuits and doughnuts can be relied upon to ease the tension.

They are comfort foods, associated with familiar experiences and carrying some soothing whiff of nostalgia. But our attachment to such foods may stem from something more powerful than misty recollections of summer afternoons in childhood. Researchers have discovered that high-energy foods — generously endowed with fats and sugar — can turn down the levels of stress hormones circulating in the body.

“Eating comfort foods may directly reflect an underlying, natural braking system for stress,” says Norman Pecoraro, a postdoctoral fellow at the University of California at San Francisco, one of the study’s authors.

Under the direction of Professor Mary Dallman, Pecoraro performed a study in rats detailing how the chronic stress hormonal cycle can be blunted by lard and sugar consumption. Twenty-four hours after being exposed to stress, the rats were prompted to eat high-energy foods. Eating them reduced immediately the rats’ levels of corticosterone; the equivalent hormone in people would be cortisol.

According to the researchers’ work, published in the Early Edition of Proceedings of the National Academy of Sciences, a metabolic signal from fat deposits may have a calming effect.

“Almost all the things that you feel are good or pleasurable — feeding, sex, drug-taking — go through the same reward pathway of the brain,” Pecoraro says.

He adds that the link between food and stress reduction is not really surprising: “It makes perfect sense in terms of evolution. The stress hormones are moving energy around your body to get you to go out and find food. Certainly in rats there is this natural rhythm that is related to foraging behaviors.”

In an eat-or-be-eaten world in which you don’t know when your next meal will be, he says, the kind of stress that prompts an animal to seek out high-energy food could well be a life-saving one.

And Pecoraro’s experiments show that it has to be the real thing — artificial sweeteners did not produce the same palliative effect as sucrose. The finding could explain why anxiety and depression are associated with binge-eating, and could illuminate eating disorders such as bulimia.

Other recent studies hammer home the message that brain chemistry appears to be instrumental in overeating. Scientists at the Brookhaven National Laboratory in New York reported recently in Synapse that people receive a kick of the brain’s pleasure chemical, dopamine, at the mere sight or smell of foods that they know to contain sugars and fats.

Dr Nora Volkow used positron emission tomography to scan human brains and found the sugary food response comparable to that of drug addicts. Whether it’s doughnuts or drugs, the same pleasure signals reinforce behaviours and generate needs.

Researchers at Princeton University found that rats which were allowed to binge on sugar experienced an increase in the number of receptors in their brains for dopamine and opiates. They became dependent on sugar and when an opiate-blocker was administered, the rats displayed symptoms of withdrawal from their brains’ own morphine, including teeth-chattering, body-quivering and anxiety.

The suggestion that junk foods and stress are wedded in an endless feedback loop, stoking unhealthy cravings, is interesting in the light of recent court cases involving fast-food manufacturers.

Even with an obvious worldwide trend towards obesity, it’s a tough task to make sugary and fatty treats look as insidious to a judge or jury as tobacco. But some scientists might argue that purveyors of junk food are exploiting dependencies arising from deep in our brain chemistry.

Is the food industry profiting from the internal reward systems that were once critical to the survival of our species? With obesity and related ills soaring everywhere, and associated medical expenses and productivity losses mounting, there is a great temptation to pass along liability.

The easy answer is to lay the blame for global corpulence at the feet of corporations. Round one in that fight, however, goes to the fast-food companies.

A lawsuit waged by a New York lawyer, Samuel Hirsch, accusing McDonald’s of false advertising to overweight youths was thrown out for a second time recently with no recourse. In limbo is another Hirsch lawsuit on behalf of an obese middle-aged man alleging that McDonald’s, Burger King, Wendy’s and KFC Corp encouraged customers to become addicted to fatty foods.

The responsibility for healthy eating would seem to have been shoved back on to the consumer’s plate. But John Banzhaf III, a professor of law at George Washington University, is undeterred, arguing that whatever the outcome of legal cases so far, the principle of the argument remains.

Perhaps food companies should start to read the neuroscience journals.

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