Washington ? Faced with their favorite foods, women are less able than men to suppress their hunger, a discovery that may help explain the higher obesity rate for females, a new study suggests.

Researchers trying to understand the brain’s mechanisms for controlling food intake were surprised at the difference between the sexes in brain response.

Gene-Jack Wang of Brookhaven National Laboratory and colleagues were trying to figure out why some people overeat and gain weight while others don’t.

They performed brain scans on 13 women and 10 men, who had fasted overnight, to determine how their brains responded to the sight of their favorite foods. They report their findings in today’s edition of Proceedings of the National Academy of Sciences.

“There is something going on in the female,” Wang said in a telephone interview, “the signal is so much different.”

In the study, participants were quizzed about their favorite foods, which ranged from pizza to cinnamon buns and burgers to chocolate cake, and then were asked to fast overnight.

The next day they underwent brain scans while being presented with their favorite foods. In addition, they used a technique called cognitive inhibition, which they had been taught, to suppress thoughts of hunger and eating.

While both men and women said the inhibition technique decreased their hunger, the brain scans showed that men’s brain activity actually decreased, while the part of women’s brains that responds to food remained active.

“Even though the women said they were less hungry when trying to inhibit their response to the food, their brains were still firing away in the regions that control the drive to eat,” Wang said.

Nora Volkow, director of the National Institute on Drug Addiction and a co-author of the paper, said the gender difference was a surprise and may be because of different nutritional needs for men and women.