Women Cannot Control Their Hunger As Well As Men, Study Shows
study at the U.S. Department of Energy’s Brookhaven National
Laboratory shows that men, but not women, are able to control their
brain’s response to their own favorite foods. The study, which
will be published online by the Proceedings of the National Academy of
Sciences the week of Jan 19, may help explain why rates of obesity and
eating disorders are higher among women than men, and why women
typically have more difficulty losing weight.
may help us understand the neurobiological mechanisms underlying the
ability to control food intake, and suggest new pharmacological methods
or other interventions to help people regulate eating behavior and
maintain a healthy weight," said Gene-Jack Wang, lead author on the
study. "The surprising finding of a difference between genders in the
ability to inhibit the brain’s response to food and hunger will
certainly merit further study."
scientists used positron emission tomography (PET) scanning to monitor
brain activity in 13 female and 10 male volunteers. In this method, a
form of glucose "tagged" with a radioactive tracer molecule is injected
into the blood stream while subjects lie in the PET scanner. The
scanner tracks the tracer’s signal to monitor the uptake and use
of the glucose by various regions of the brain. All study subjects were
of normal body weight and had fasted for nearly 20 hours before each of
three separate scans, performed in random order.
image shows the change in brain metabolism when subjects were asked to
inhibit their response to food during food stimulation compared with
when they were not told to inhibittheir response. Two brain sections at
different levels of the brain are shown for each group (women, men, and
women vs. men). Top row, women: No color indicates that women had no
significant differences in brain activity between the two conditions.
Middle row, men: Blue colored areas were significantly less active when
men were told to inhibit their response to food than they were without
inhibition. Third row, women vs. men: Orange color indicates areas
where men showed greater decrements with inhibition than women. These
brain regions are involved in emotional regulation, conditioning, and
the motivation to eat.
On one scan
day, subjects were presented with their favorite foods — from
bacon-egg-and-cheese sandwiches to pizza, cinnamon buns, barbecue ribs,
and chocolate cake — warmed, if appropriate, to enhance the
enticing aromas and taste. During the scan, subjects were asked to
smell, taste, observe, and react to the food, but not eat it. On
another day, they were instructed to inhibit their desire for food
prior to being tempted with the same foods. A control scan with no food
was performed on another day.
volunteers were also asked to rate the foods and describe their
feelings of hunger and their desire to eat during the scans when food
In both men
and women, a variety of brain areas associated with emotional
regulation, conditioning, and motivation "lit up," indicating increased
metabolic activity in those regions, in response to the tempting foods
when compared with the no-food scans — a finding consistent with
earlier work using the same setup at Brookhaven Lab. When asked to
inhibit their response to food, both men and women described themselves
as less hungry and less interested in eating than when they
weren’t trying to inhibit their response. But only the men showed
a relative decrease in activity in the food-activated brain regions
during the scan when they were asked to inhibit their response.
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. "In contrast,
men’s brain activity decreased along with their self-reports of
hunger during the scan when they were asked to keep their hunger in
researchers believe this is the first study to document such a
gender-specific disconnect between subjective reports of an emotional
or motivational state and the associated pattern of brain activity.
"This may indicate a difference between the genders in the ability to perceive and respond to internal body signals," Wang said.
of a lack of response to inhibition in women is consistent with
behavioral studies showing that women have a higher tendency than men
to overeat when presented with palatable food or under emotional
distress," Wang said. "This decreased inhibitory control in women could
be a major factor contributing to the observed differences in the
prevalence rates of obesity and eating disorders such as binge eating
between the genders, and may also underlie women’s lower success
in losing weight while dieting when compared with men."
in sex hormones, such as estrogen, may underlie these gender
differences and merit further exploration. Sex hormones are known to
directly influence food intake, body weight, and fat distribution, as
well as the signaling of other molecules involved in regulating eating
behavior, the researchers said. This study did not control for
variations in the menstrual cycle of the female research subjects.
woman’s menstrual cycle can be an important factor in
responsiveness to reward and in successful quit attempts for smoking,"
said National Institute on Drug Abuse (NIDA) Director Nora Volkow, who
was a collaborator on this study. "Its role in inhibiting food-related
brain activation will be important to address in future studies."
This study was funded by the National Institute on Drug Abuse, the National Institute on Alcohol Abuse and Alcoholism, and by the General Clinical Research Center of Stony Brook University.