Men have more willpower than women when it comes to resisting food, a small new study suggests.

"We didn’t expect such striking differences between males and females," study co-author Nora Volkow, director of the National Institute on Drug Abuse, tells "Men were able to inhibit their desire for food . . . and women weren’t able to do so."

Scientists had 13 women and 10 men who had fasted overnight look at, smell and taste – but not dig into — goodies like pizza, burgers and cake. They then told the subjects to practice "cognitive inhibition" (read: to try to convince themselves they weren't really hungry) and measured their brain activity using positron emission tomography (PET) scanning. (PET scans measure increases in blood flow linked to brain activity.)

Both sexes reported they felt less hungry when they were trying not to be, according to results published in this week’s Proceedings of the National Academy of Sciences. But the scans suggested that only the guys were able to control their desire to eat. On average, the men showed less activity in the limbic system (the brain’s emotional center that controls the drive to eat) when told to inhibit their craving for food than they did when they weren't told to control their hunger. There was no difference, however, in the women's brain activity.

Specifically, there was a decline in activity in the men's amygdala (an emotional memory region), striatum (a motivation region), hippocampus (another memory area), the orbital frontal cortex, insula and anterior cingulate (which together regulate inhibition, or self-control around food), says study co-author Gene-Jack Wang, a senior scientist at Brookhaven National Laboratory in Upton, N.Y.

Wang and Volkow acknowledge that their findings have limitations. Their sample size was tiny, and the study didn't prove that women are actually more likely to chow down in the face of temptation, since they weren’t given the opportunity. The next step, Volkow says, is to examine "to what extent your subjective perception of whether you can control your hunger or not will predict whether you eat or not. You’d want to determine if, indeed, women will be much less likely to inhibit the food if you put it in front of them. I’d predict that, overall, males may be better."

Some 35 percent of U.S. women suffer from obesity, compared with 33 percent of men, according to the Centers for Disease Control and Prevention (CDC). But women are also disproportionately represented among anorexics, who restrict their food intake to the detriment of their health.

That reality doesn’t challenge the new findings, Volkow says. "For reasons we don’t understand, the female brain is more vulnerable to disorders of feeding, and that can reflect itself in excess or in a compulsion to not eat," she says. "Anorexics are fixated with food, but it is the control over that fixation that becomes reinforcing and motivates their behavior."

Image © iStockphoto/Dean Turner