Fasting Impacts Brain’s Ability to Resist Unhealthy Foods

Kathleen Page, assistant professor of medicine at the University of Southern California (USC) Keck School of Medicine’s (Los Angeles, USA) division of endocrinology while at Yale University (New Haven, CT, USA), indicated that the area of the brain regulating impulsive behavior is less able to fight temptation for a slice of pizza or a bunch of chocolate chip cookies when blood glucose is low. Glucose is the brain’s primary fuel source.

Dr. Page is one of the lead authors of the study, which will is published online September 2011 in the Journal of Clinical Investigation. “We’ve all experienced it--we skip breakfast, we’re starving at lunch and the first thing we usually find to eat is unhealthy,” he said. “We know that a drop in blood sugar drives people to eat, but we didn’t know the relationship of how the brain responds to low blood sugar and the foods we desire.”

Dr. Page’s team studied lean and obese individuals whose blood sugar had been reduced intravenously with insulin. Employing functional magnetic resonance imaging (fMRI), the researchers looked at which areas of the brain were activated when the test subjects viewed pictures of different kinds of foods, from fatty foods like cake and ice cream to more healthy choices such as salads and fruit. The study participants rated their desire for the foods.

All the study participants desired the higher-calorie foods more when glucose levels dropped below normal. The brains of obese people in particular showed a lack of inhibition of impulsive desire for food. “The prefrontal cortex is the part of the brain that says ‘stop eating,’” Dr. Page said. “When blood sugar levels are low, that area of the brain is less activated. Obese individuals lacked prefrontal brain activation even when sugar levels were normal. We don’t know if obesity changes the way the brain responds or if it responds this way because of obesity.”

Though more research is needed to determine reasons that obese people’s brains respond differently to low blood sugar, the message for most people is to give the brain a steady supply of fuel to prevent overeating. “Eating healthy food that maintains glucose levels is the key,” Dr. Page concluded.

Related Links:
University of Southern California Keck School of Medicine
Yale University