hungry men can, a brain imaging study suggests.
The finding may explain why women are more prone to emotional eating and why
women are less likely than men to lose weight while dieting.
"Women have a much stronger reaction to food, such that whether they try
to inhibit their desire or not, they have stronger signal [in the part of the
brain that controls hunger perception and desire to eat]," study leader
Gene-Jack Wang, MD, tells WebMD.
Wang, chairman of the medical department of Brookhaven National Laboratory,
Upton in N.Y., and colleagues have been using state-of-the-art brain imaging to
learn which parts of the brain are involved in eating behaviors.
They have previously shown that obese people are less able than others to
sense when their stomachs are full. Recently, they have looked at what happens
in the brain when a hungry person gets to see, smell, and taste -- but not eat
-- favorite foods.
In some of these studies, they saw very strong signals in parts of the brain
involved in emotional regulation and motivation. But in other studies, the
signals weren't so strong. Wang suspected this might be because of differences
between how men and women react to food.
So they tested 13 women and 10 men with PET brain scans. To make sure they
were hungry, study participants fasted for 18 hours before scanning. And to
make sure they were tempted, the researchers made the participants' favorite
foods: bacon/egg/cheese sandwiches, cinnamon buns, pizza, cheeseburgers, fried
chicken, lasagna, barbecued ribs, ice cream, brownies, and chocolate cake.
During scanning, participants were able to see and smell the food. They even
got tastes, applied to their tongues with a cotton swab. To make sure they
stayed tempted, researchers brought them new hot food every four minutes.
But subjects didn't get to eat until the 30-minute scans were completed, and
only after they completed a quiz on their feelings of hunger, desire for food,
Before their second round of scans, participants were asked to practice
ignoring the food or shifting their thoughts away from it. During this phase of
scanning, they were asked "to inhibit their desire for food and suppress
their feelings of hunger."
That worked pretty well for the men. Their brain scans showed much less
hunger-related activity when they tried to suppress their desire for food.
That didn't happen for the women, at least not as a group. Although some
women were better than some men at suppressing food desire, overall the women's
brains showed just as much hunger-related activity when they tried to hold down
Are the findings plausible? WebMD asked Rexford S. Ahima, MD, PhD, director
of the obesity center at the University of Pennsylvania's Institute for
Diabetes, Obesity, and Metabolism. Ahima is an expert in the brain circuits
responsible for feeding behavior and body weight regulation.
"More and more we see there is a structural basis for why we eat the way
we do. Maybe our brains are hardwired to predetermine the way we eat,"
Ahima says. "The interesting thing about the Wang study is that when they
present food to people and ask them to consciously inhibit the urge to eat, men
are better able to do it than women."
Ahima notes that the study only shows men to be better at inhibiting their
brains' response to food. But can men really resist emotional eating better
than women can? That, he says, will have to be tested directly.
Sex Hormones May Affect Hunger
Why do men's and women's brains respond differently? Wang and Ahima suspect
that female sex hormones play a major role.
"There is a link between female hormones tending to promote weight gain
and overeating," Ahima says. "There are some women who tend to binge
eat in synch with their menstrual cycles. And look at pregnancy -- it maks
some women overeat, but some do not. So while there may be overall differences
in terms of gender, this may differ for individuals."
Wang suggests that women may have evolved to seek food more avidly than men
"There could be evolutionary needs for that, because women have a very
important mission: They have to carry the baby," Wang says. "And for
most of human history, you could never get enough food to eat. Now that's no
longer a problem in developed countries -- but now this brain circuit is a
problem when we are surrounded by attractive, high-calorie foods."
The solution, Wang says, is for people who find themselves unable to control
their eating to keep filling, low-calorie foods close at hand.
"Our lifestyle now is so much different from that of our
grandparents," Wang says. "Our jobs and our living status is very
stressful. So when we see food we eat it, because we want to do something to
compensate for our problems. Inhibition control is very important -- but if you
can't have it, surround yourself with nutritious foods."
Wang's study appears in the Jan. 15 early online edition of the
Proceedings of the National Academy of Sciences.
By Daniel DeNoon
Reviewed by Louise Chang
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