Comfort food calms, with weighty effect.

The sweet and fatty foods that people often turn to in times of stress might in fact relieve anxiety. That's the good news in an innovative biological theory of people's responses to stress. The bad news is that for those with chronic stress, extra servings of comfort food come with potentially dangerous baggage--extra fat around the abdomen.

Chronic stress, such as financial worries, is less well understood than are intermittent bouts of acute stress. For example, scientists know that when a cat is suddenly attacked by a dog or a person prepares to give a speech, the adrenal gland pumps up production of stress hormones, including those known as glucocorticoids. When present at high-enough concentrations, glucocorticoids provide feedback to the stress-response system, eventually shutting it down.

However, it's unclear how the stress response is controlled in animals that are anxious for days at a time. In an upcoming Proceedings of the National Academy of Sciences, physiologist Mary F. Dallman of the University of California, San Francisco and her colleagues aim to close that knowledge gap.

Drawing on their rat studies and experiments done by others, the scientists propose that glucocorticoids work differently in the long term than they do in the short term. When chronically present in the brain and body, the hormones maintain the stress response instead of shutting it down. At the same time, they drive animals to seek out pleasurable foods and direct the added calories to accumulate as abdominal fat.

However, there is a brake on the process, at least in animal experiments. That extra fat eventually checks the glucocorticoids' alarmist effects and tells the brain to take it easy again.

Results from several experiments with rats support this view, the scientists say. In one of them, Dallman and her colleagues simulated chronic stress by increasing the brain concentration of a rodent version of the glucocorticoid called cortisol. As cortisol concentration rose, the rats responded by drinking increasingly more sugar water, eating increasingly more lard, and gaining abdominal girth.

In another experiment, the researchers found that rats with extra padding produce less-than-average concentrations of a brain chemical that triggers early molecular events underlying the stress response.

"If you put on some extra weight, there seems to be some sort of signal that says things are better," says Norman C. Pecoraro of UC-San Francisco, a coauthor of the paper. While Dallman and her coworkers don't know what signal the abdominal fat sends, they suspect it's involved with the regulation of metabolism.

The model "puts a new and more meaningful slant on what we mean when we talk about 'comfort foods,'" says Bruce S. McEwen of Rockefeller University in New York. "These may actually calm down an important brain system linked to anxiety."

In a fast-paced society where food is easy to get, glucocorticoid action probably causes chronically stressed people to take in extra calories and to gain weight, says McEwen.

"People are somehow stressed, and they are self-medicating because food is available," adds Pecoraro.

"We also eat sugar and fat because they are good tasting and cheap," notes Adam Drewnowski of the University of Washington in Seattle. The stress response isn't the only brain pathway that controls consumption of sweet and high-fat foods, he adds.

Whatever accounts for the urge to eat a big helping of macaroni and cheese, it's best not to indulge every day. The abdominal weight gain that Dallman and her colleagues have linked to glucocorticoid action increases the risk of heart disease and diabetes.