Saturday October 18, 2008 (foodconsumer.org) -- A new
study published in the Oct 17, 2008 issue of the journal Science suggests that
a gene variant has something to do with the obesity epidemic.
But a health observer quickly warned that the
genetic effect on the risk of obesity if there is any should be small and
people can adjust their lifestyle including their diet to get their weight
The study led by Eric Stice, PhD, of the Oregon Research
Institute and colleagues from Yale University and the University of Texas at
Austin found some evidence to support the theory that "individuals may
overeat to compensate for a hypofunctioning dorsal striatum, particularly those
with genetic polymorphisms thought to attenuate dopamine signaling in this
The researchers found females with decreased striatal
activation in response to the milkshake in the study were at increased risk of
weight gain after one year.
risk was even greater in those who had both decreased striatal activation and
the A1 allele.
The study involved two sub-studies. One enrolled 43
female college students ages 18 to 22 with a mean body mass index of 28.6 while
the other involved ages 14 to 18 with a mean BMI of 24.3.
For the study, Stice and colleagues let subjects eat fat
and sugar loaded milkshake and measured the striatal activation in response to
food intake in the brain using a technique called functional Magnetic Resonance
Subjects were also
tested for Taq1A1 allele.
Early studies found people with this gene variant tend to
have a low number of dopamine D2 receptors, meaning they are less likely to get
satisfied with the amount of food they eat which would otherwise satisfy those
who do not have the gene variant.
Stice and colleagues found females who carry a genetic
variation and a weakened "reward circuitry" in their brains or
decreased striatal activation in response to food intake were significantly
more likely to gain weight after one year.
The researchers said the finding demonstrated that people
who have the gene variant and a blunted response to the pleasure from eating
food would have to eat energy-dense food (fat and sugar with much fiber) to get
satisfied, leading to an increase in the risk of becoming obese.
In an interview with the journal Science, Dr. Stice said
his group just completed a new study to see dietary intervention would
counteract the effect of the gene variant. The data did not come out, but he said
"you could use either behavioral or pharmacological interventions to try
to correct this blunted striatal response to food received."
Another study published in the Sep 30, 2008 issue of
Nutrition also suggests that just because you have the Taq1A gene variant you do
not necessarily have to become obese.
The study led by Barnard ND and colleagues from George
Washington University School of Medicine showed at least white people who were
positive for Taq1A actually reduced fat intake after 74 weeks on a vegan diet.
But for blacks, the vegan diet did not make
much of a difference.
The study did not say whether this vegan diet helped
subjects’ weight loss among those who reduced fat intake.
But at least, the results suggested that the
white Taq1A carriers do not have to turn to a high fat diet for the eating
Although the Stice's study suggests that the gene variant
carriers are more likely to over-eat energy dense foods, which could be a cause
for obesity, the caloric intake alone does not determine the weight
Colin T. Campbell, Ph.D., a distinguished nutrition
professor at Cornell University said Chinese people in rural areas eat 400 more
calories than their American counterparts, but few of them are obese.
He noticed two things are different; the
Chinese in such areas eat mostly a whole foods, plant-based diet.
In their diet, fat and meat are low while the
bulk is grain products and vegetables. They are also more physically active.
Dr. Campbell said a whole foods, plant-based diet plus moderate
amounts of physical activity are the only solution to maintaining healthy
weight although people who have some genetic variant need to work hard to keep
their weight under control.
this whole foods plant-based diet is more satisfying and the eaters can eat
whatever amounts they want to, but are unlikely to gain weight as showed in
many early studies.
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