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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.
The volunteers were also
asked to rate the foods and describe their feelings of
hunger and their desire to eat during the scans when food
was presented.
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.
“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. “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 check.”
The 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.
“The finding 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.”
Differences 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.
“A 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. |
