Gobbling down that handful of potato chips when you're under stress may have more to do with hormones than hunger, according to a preliminary study by Yale University researchers.

The study, reported last week at a meeting of the Society of Behavioral Medicine in New Orleans, suggests a possible genetic answer as to why some people, especially women, eat more and gain weight during times of high stress while others eat less and lose weight.The researchers examined the eating habits of 60 women and measured the levels of the hormone cortisol in their saliva.

Scientists have known for some time that when people experience stress, many physiological changes occur, including a change in heart rate and a flux in cortisol levels. The question is what precipitates changes in eating patterns.

"The study was really just a first step in starting to help us untangle the biology from the psychology," said psychology professor Kelly Brownell, director of the Center for Eating and Weight Disorders at Yale.

The test subjects - all healthy women ranging in age from 30 to 45 - were given a variety of stressful tasks to perform with unrealistic time constraints. The tasks included counting backwards, trying to solve an unsolvable puzzle, and giving a speech.

During the tasks, the researchers periodically measured cortisol in the women's saliva. After the exercises, the women were allowed to snack without restraint on high-fat or low-fat foods.

The researchers found that the women who secreted the most cortisol ate the most high-fat food after stress. The women who didn't eat any high-fat food had secreted the least amount of cortisol.

"Cortisol is linked both to emotions and eating," researcher Elissa Epel said. "We know that during chronic stress, if we have high cortisol and high insulin, this combination tells the body to store fat to stock up resources for hard times ahead."

The researchers plan to publish their findings in a peer review journal later this year.

Catherine G. Greeno, a psychologist at the Western Psychiatric Institute and Clinic at the University of Pittsburgh Medical Center, said the study was "important basic research," but cautioned that other hormones also may have an effect on eating.

Neil Grunberg, professor of a neuroscience and psychology at the Uniformed Services University in Bethesda, Md., called the Yale study "overly simplistic."

He said a variety of psychological factors and other chemicals in the body may have important roles in determining food consumption during times of stress.

However, Bruce McEwen, professor of neuroendocrinology at Rockefeller University in New York, said the Yale findings "make a lot of sense.

"Cortisol is certainly one of the major players. It may not be the final pathway, but it's an important link in the sequence," he said.