The Brain Can Show Hunger

Fructose and glucose affect blood flow to hunger areas of the brain differently

(RxWiki News) There's a reason why eating bread and potatoes can be so much more satisfying compared to fruit. Blood flow to the brain can show it.

Ingesting glucose but not fructose reduces blood flow to the brain, specifically the regions in charge of appetite and mood, according to a recently published study.

The findings help show what kinds of foods leave the body feeling full or still hungry, researchers said.

"Eat in moderation."

The aim of the study, led by Kathleen Page, MD, of Yale University School of Medicine, and colleagues, was to see which factors are behind the link between consuming fructose, which is a simple sugar found in fruits and plants, and gaining weight.

The study included 20 healthy adults who had images of their brain taken during two magnetic resonance imaging (MRI) sessions.

At one MRI session, patients drank a concoction with fructose. To compare the effects, patients consumed glucose, another kind of sugar, during the other session. The patients did not know which of the two they were receiving at each session.

Researchers found that blood flow to the hypothalamus, which is responsible for hunger and mood, was significantly reduced after ingesting the glucose versus the fructose. This means that the body felt satiated and satisfied.

By drinking the glucose, brain connectivity increased between the hypothalamus and other regions of the brain, according to the researchers.

The fructose on the other hand lowered blood flow to fewer areas of the brain, which means that fewer satiety hormones circulated around compared to those caused by the glucose.

"Increases in fructose consumption have paralleled the increasing prevalence of obesity, and high-fructose diets are thought to promote weight gain and insulin resistance," researchers wrote in their report.

"Thus, fructose possibly increases food-seeking behavior and increases food intake," researchers said.

The authors noted that MRIs do not directly measure neuron activity in the brain; rather, they show changes in blood flow and the influx of oxygen in the blood.

The study was published in the January 2 issue of JAMA. The National Institutes of Health and the Yale Center for Clinical Investigation, which was supported by the Clinical Translational Science Award, funded the study. The authors do not report any conflicts of interest.

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Review Date: 
December 30, 2012