Study: Obese People May Find Sensory Properties of Food More Rewarding

The parts of the brain responsible for sensation in the mouth, lips and tongue are more active in obese people, and they may eat too much because they find food more palatable, according to researchers at the Brookhaven National Laboratory.

"This enhanced activity in brain regions involved with sensory processing of food could make obese people more sensitive to the rewarding properties of food, and could be one of the reasons they overeat," said Dr. Gene-Jack Wang, lead author of the study.

Obese people have fewer brain receptors for dopamine, the neurotransmitter responsible for the feelings of satisfaction and pleasure. Researchers speculate that obese people may eat to stimulate their underserved reward circuits.

Overall brain metabolism does not differ between obese and normal weight study participants. However, researchers wondered whether obese people have enhanced metabolic activity in specific brain regions, including those involved in the sensory processing of food.

Researchers used positron emission tomography (PET) to measure regional brain metabolism in 10 severely obese and 20 normal-weight controls. The volunteers were injected with a radioactively labeled form of glucose. The radiotracer glucose concentrates in the regions of the brain where metabolic activity is highest. The PET scanner picks up the radioactive signal to show where the glucose is located.

The highest amount of activity in the obese volunteers was found in the brain's parietal cortex, where input from the mouth, lips and tongue is received as well as an area involved with perception of taste, according to the study to be published in the journal NeuroReport.

"The enhanced activation of these parietal regions in obese subjects is consistent with an enhanced sensitivity to food palatability, which is likely to increase the rewarding properties of food," said Wang.

Other sources:Brookhaven National Laboratory