A brain region in charge of controlling impulsively is smaller in obese teens than in lean ones, according to a new study.
The results suggest the bad eating
habits that lead to obesity aren't simply due to a lack of
self-restraint, researchers said. Rather, the smaller size of this
impulse-control region in the brain might predispose certain children to
gain weight. Or the obesity itself may even influence brain size, which in turn fuels uninhibited eating.
"It's not as simple as kids who have weight problems
simply don't
have enough willpower to actually lose weight," said study researcher
Dr. Antonio Convit, of the New York University School of Medicine and
the Nathan S. Kline Institute for Psychiatric Research in NY.
"It could be that their brains are either wired differently, or damaged in a particular way that leads them to gain weight from overeating," he said.
Convit
and his colleagues administered questionnaires on eating behaviors to
91 adolescents. The teens were on average 17 years old; 37 were normal
weight and 54 were obese. The obese teens had an average body mass
index, or BMI, of 39, and weighed 300 pounds on average.
The researchers scanned the teens' brains using magnetic resonance
imaging (MRI), and the teens completed several cognitive tests designed
to see how well a particular brain region, known as the frontal lobe,
was working. The frontal lobe is essential for planning, self-monitoring
and modifying behavior. People who have damage to this area are less
likely to have good impulse control, Convit said.
As expected, the obese teens were more impulsive in their eating
behaviors. They also had a smaller orbitofrontal cortex, part of the
frontal lobe, and performed worse on the cognitive tests than lean
adolescents did. In addition, the adolescents with a smaller
orbitofrontal cortex were more likely to eat impulsively, known in
psychology as "disinhibited" eating.
Because the children came from families with the similar income
levels , it's unlikely that their socioeconomic class played a role in
their performance on the cognitive tests. And the results held even
after the researchers took into account the participants' blood
pressure, which may influence frontal lobe function, Convit said.
The researchers noted the study only shows an association, and not a
cause-effect link. And they don't know whether it's obesity that may
lead to a smaller frontal lobe, or the small frontal lobe that may
contribute to obesity.
But there is a plausible explanation for how obesity changes the brain.
Obesity is known to cause changes to the immune system, boosting inflammation in the body.
This increased inflammation may impact the brain and "lead to a vicious
cycle, where the obesity leads to inflammation, which damages certain
parts of the brain, which in turn leads to more disinhibited eating and
more obesity," Convit told MyHealthNewsDaily.
And while the obese adolescents were not diabetic, they had elevated fasting insulin levels,
which may also harm the brain. Insulin is a hormone that allows cells
to take up sugar, or glucose, from the blood. Obese individuals, because
they have insulin resistance, often need to produce more of it to keep
their blood sugar levels normal.
The study was presented today (Oct. 28) at the American Academy of Child and Adolescent Psychiatry Meeting in New York City.