For longer versions of these and other
Body & Brain stories, visit www.sciencenews.org
Obesity impairs brain performance
By Janet Raloff
Obesity subtly diminishes memory and
other features of thinking and reasoning
even among seemingly healthy people,
new research shows. At least some of
these impairments appear reversible
through weight loss. One likely mech
anism for those cognitive deficits appears
to be damage to the wiring that links the
brain’s informationprocessing regions.
Studies have shown that individuals
with diseases linked to obesity, includ
ing cardiovascular disease, hypertension
and type 2 diabetes, don’t score as well
on cognitive tests as less hefty people do.
To test whether weight alone — and not
disease — might be partially responsible,
John Gunstad of Kent State University
in Ohio and colleagues gave a series of
cognitive tests to 150 obese volunteers.
Those participants weighed on average
just under 300 pounds, although some
were much heavier. Twothirds would
shortly undergo weightloss surgery.
Scores on the tests were assessed
against those of healthy people in the
Brain Resource International Database.
On average, obese participants initially
performed on the low end of the normal
range for healthy people, Gunstad says.
But nearly onequarter of the obese
participants’ scores on memory and
learning actually fell within what
researchers consider the impaired range.
Tested 12 weeks after bariatric sur
gery— when most had shed some 50
pounds—the lighter but still heavy
patients scored substantially better.
Most now performed “within the aver
age or greaterthanaverage range for all
cognitive tests,” the researchers reported
online last October in Surgery for Obesity
and Related Diseases. Those who didn’t
have surgery — or lose weight — per
formed worse on the second test.
on who mice woo
Males court both sexes when
deprived of serotonin in brain
the lab isn’t equivalent to human
homosexuality. And what, if anything,
serotonin has to do with human sexual
behavior is still an open question.
In the study, male mice genetically
engineered to lack serotoninproduc
In tests where both a male
and a female mating partner
were present, nearly half of
the serotoninlacking males mounted
the male first, report researchers led by
Yi Rao of Peking University in Beijing.
These mice were also more likely
than normal mice to emit ultra
sonic squeaks — a type of mouse love
song — toward other males and spent
equal time sniffing male and female
odors. Some of the altered sexual behav
iors could be reversed by restoring
serotonin to the brain, the team found.
Psychiatrist and sexualresearch sci
entist Milton Wainberg of Columbia
University says that it’s too simplistic to
apply the experimental results to human
sexuality. “These mice are not gay,” he
says. “These mice have a disease that
makes them do one behavior, which ...
can be thought of as a homo
sexual behavior, but it’s not
The new result “opens
now quite a lot of fascinat
In humans, antidepressant drugs
that increase active serotonin levels
in the brain do have some sexrelated
side effects. Some can decrease libido
in people. Yet there’s no evidence that
serotonin has any influence on sexual
orientation, Wainberg says.
By Laura Sanders