MONDAY, Sept. 19 (HealthDay News) -- A new study links low blood
sugar in obese people to a greater desire within the brain for
high-calorie foods, a finding that offers insight into why people
who become overweight tend to stay that way.
"Their brains may be driving them to eat more and desire these foods more, and that may promote overeating," explained study author Kathleen A. Page. "We don't know if that's a consequence of obesity or contributes to the obese state. Are their brains wired differently from the start? Or does that happen after they become obese?"
Whatever the case, the research points to the importance of
keeping blood sugar levels stable, said Page, an assistant
professor of medicine at the University of Southern California.
Levels of sugar in the blood are directly linked to energy, and
those levels often drop after eating lunch and cause a
mid-afternoon slump. Blood sugar levels also drop in the morning,
and after you eat a high-sugar food, Page said. In that case, the
body's processing of the excess sugar can cause levels to dip.
In the new study, published in the Sept. 19 online issue of
The Journal of Clinical Investigation, Page and colleagues tried to figure out if dips in blood sugar affect obese people differently than those who aren't overweight.
In the study, functional MRI scanners monitored the brains of
five obese and nine non-obese people as researchers adjusted the
levels of sugar in their blood, changing them from normal to low.
At the same time, the researchers showed them pictures of foods
that are low-calorie (various fruits and vegetables, tofu,
soybeans, salads) and high-calorie foods (brownies, donuts, fried
chicken, steak, ice cream and more).
The researchers found that the obese people had less brain
activity in the area known as the prefrontal cortex, where powers
of inhibition (choosing not to do things) are based, even when
their blood sugar levels were normal. "That implies that obese
people may have a harder time fighting off the urge to eat,
especially when their sugar levels are below normal," Page
Jean-Philippe Chaput, an assistant professor at the University
of Ottawa's School of Human Kinetics, said the research is relevant
because it provides greater understanding into how blood sugar
affects eating habits. "Future obesity treatments will need to take
that aspect into account if we want to improve our chances of
success," Chaput said.
But Dr. Marc-Andre Cornier, an associate professor of medicine
at the University of Colorado, cautioned that the study doesn't
definitively link blood sugar to hunger. "The lower glucose may
have impacted another factor that in turn was responsible for the
effects," he said, adding that it's "pure speculation" to say that
keeping blood sugar levels stable after meals will reduce
For more about
obesity, try the U.S. National Library of Medicine.
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