January 20 (HealthDay News) -- New research on the brain suggests that women unconsciously have a tougher time resisting their favorite foods than men do.

"This gives us another piece to put into this puzzle," said Dr. Gene-Jack Wang, the study's author, who speculated that women may have more trouble saying no to food because they sometimes have to eat for two.

"Maybe evolution leads them to this because of their important mission to have a baby," said Wang, a senior scientist at Brookhaven National Laboratory and professor of psychiatry at Mount Sinai School of Medicine in New York.

According to Wang, the new study aimed to understand why some people don't stop eating when they're full. Your body tells you that you've eaten enough by sending a signal to your brain from the gut, he explained, "but if you go to the buffet, sometimes you just cannot stop."

This wasn't a big problem throughout history because people rarely had a chance to eat more than they needed, Wang said. But modern society has changed that, he said, especially over the past 30 to 40 years as obesity has become much more common in the United States.

For the study, which appears in this week's issue of the Proceedings of the National Academy of Sciences, the researchers asked 13 women and 10 men about their favorite foods. The participants said they liked a variety of dishes and desserts, including lasagna, pizza, brownies, ice cream and fried chicken.

Then, after they fasted for 20 hours, the researchers presented them with their favorite foods; the dishes were even warmed up, if appropriate, to make them more tempting. The men and women were allowed to smell and taste the food but not eat it. Then, in an experiment, they were told to try to inhibit their desire to eat the food.

Meanwhile, PET scans examined their brain activity.

The researchers found that certain areas of the brain became more active in both the men and women when they were tempted with food. The brain areas that lit up control emotions such as motivation.

Also, both men and women succeeded in making themselves feel less hungry by inhibiting their desire to eat the food. But the brain scans suggested that the women's brains were still acting as if they were hungry.

In other words, the women may have thought they were less hungry, but their brains didn't seem to be entirely on board.

What's going on? Hormones could play a factor in women, Wang said, because they need to eat more when they're pregnant.

The research could help scientists understand why some people can't resist certain kinds of high-calorie food, Wang said. "Some people cannot inhibit themselves, and we need to help those people."

SOURCES: Gene-Jack Wang, M.D., senior scientist, Brookhaven National Laboratory, Upton, N.Y., and professor, psychiatry, Mount Sinai School of Medicine, New York City; Jan. 19, 2008, Proceedings of the National Academy of Sciences