More Clues About Obesity Revealed By Brain-Imaging Study [Your Tax Dollars At Work]

UPTON, NY -- The idea that obese people eat too much because they find food more palatable than lean people do has gained support from a new brain-imaging study at the U.S. Department of Energy's Brookhaven National Laboratory. The study reveals that the parts of the brain responsible for sensation in the mouth, lips, and tongue are more active in obese people than in normal-weight control subjects.

"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 Brookhaven physician Gene-Jack Wang, lead author of the study.

Wang acknowledges that obesity is a complex disease with many contributing factors, including genetics, abnormal eating behavior, lack of exercise, and cultural influences, as well as cerebral mechanisms, which are not yet fully understood. In a recent study, he and his team found that obese people have fewer brain receptors for dopamine, a neurotransmitter that helps produce feelings of satisfaction and pleasure, implying that obese people may eat to stimulate their underserved reward circuits, just as addicts do by taking drugs.

In that study, overall brain metabolism did not differ between obese subjects and normal-weight controls. But because the sensory appeal of food can be so important in triggering the urge to eat, Wang and his team wondered whether obese people might have enhanced metabolic activity in specific brain regions, particularly those involved in the sensory processing of food.

To measure regional brain metabolism, the scientists used positron emission tomography (PET) after injecting volunteers (10 severely obese and 20 normal controls) with a radioactively labeled form of glucose, the brain's metabolic fuel. Known as FDG, this radiotracer (invented at Brookhaven) acts like glucose in the brain, concentrating in regions where metabolic activity is highest. The PET scanner picks up the radioactive signal to reveal where the FDG is located.

The scientists used a computer program to average the PET data from the subjects within each group, and then compared the obese subjects' average with the normal subjects' result. The program produced three-dimensional images highlighting areas where the obese group had higher metabolic activity than the normal-weight group. v

The scientists then superimposed these images onto a magnetic resonance image (MRI) of the whole brain, as well as a diagram of the brain's somatosensory cortex, known as a homunculus. A homunculus graphically illustrates the relative number of sensory nerves innervating various parts of the body as well as where the input from these nerves is received on the somatosensory cortex.

The overlapping images revealed "hot spots" -- indicating obese subjects' higher metabolic activity -- in the regions of the parietal cortex where somatosensory input from the mouth, lips, and tongue is received. This is also an area involved with taste perception.

"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," Wang said.

Taken together with the earlier results on deficient reward circuits, this enhanced sensitivity could account for the powerful appeal and significance that food has for obese individuals.

The findings also suggest that pharmacological treatments known to decrease palatability might be useful along with behavioral therapies in reducing food intake in obese subjects.

This work was funded by the U.S. Department of Energy, which supports basic research in a variety of scientific fields, and the National Institute on Drug Abuse.

http://www.bnl.gov/bnlweb/pubaf/pr/2002/bnlpr052002.htm and http://www.bnl.gov/bnlweb/pubaf/pr/2001/bnlpr020101.htm

The U.S. Department of Energy's Brookhaven National Laboratory (http://www.bnl.gov) conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies. Brookhaven also builds and operates major facilities available to university, industrial, and government scientists. The Laboratory is managed by Brookhaven Science Associates, a limited liability company founded by Stony Brook University and Battelle, a nonprofit applied science and technology organization.

Editor's Note: The original news release can be found at http://www.bnl.gov/bnlweb/pubaf/pr/2002/bnlpr062002.htm

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Note: This story has been adapted from a news release issued by Brookhaven National Laboratory for journalists and other members of the public. If you wish to quote from any part of this story, please credit Brookhaven National Laboratory as the original source. You may also wish to include the following link in any citation:

Well DUH.

I'm fat because I eat too much, and I eat too much because I LIKE FOOD! May I now have a $10 million grant?...

Dorothy Parker had it right: "Food was the first thing I ever liked that liked me back," and in my case roughly the only thing!...

--Boris

I had a genetics professor in college that framed obesity in a light that made sense to me. People who put on weight easily these days are decended from very successful survivors of long ago. These are people who made it thru famines and hard times while people around them fell aside. Modern technology has rendered these genes impractical and deadly to the bearers today.
It's so easy to hate and despise people that are heavy. Are there any easier targets?

As a side note, I don't think overeating has nearly as much to do with the modern obesity problem as lack of exercise. My father did hard physical labor his entire life as a farmer. The minute he retired and moved to town he started putting on weight. He was a lean 165 lbs his entire life, but now is a 240 lb man who does little outside of drinking coffee and looking out the window.

It's so easy to hate and despise people that are heavy. Are there any easier targets?

I don't think anyone "hates" a person for being overweight. I do think they wonder why the person refuses to be accountable for their own actions.
If I gain any weight , I cut back my serving size. That way I don't feel deprived, and I don't starve to death on lettuce and water, either.

I grew up as a fat kid, and believe me, it felt like hate to me, both from adults and other kids.

Maybe they found you disgusting, but I'm sure they didn't hate you as a person. They probably saw you as a food glutton. No offence, honest. As a thin person on purpose, I never understood why large people do that to themselves. Why not eat less if it's a problem? I don't understand.

Disgust? Hate? All the same to a kid. All bad. But I suppose a kid should know better than to be overweight. I'm not sure why a kid would do that to himself. Perhaps they like the attention they get? It's ok for me though. During the summer between my 8th and 9th grade, I spent a whole summer unloading and stacking railroad ties by hand. I also got a real good dose of testosterone and grew to 6'3, and eventually to 6'6". I came back to school that fall as the strongest, biggest, and meanest SOB in the school. Fear is a hell of a motivator for people to be civil. If I could give one gift to every fat kid in the world it would be a set of weights.

That is the problem,,thin people don't understand fat people cause thin people aren't wired the same way. Now I am medium, neither thin nor fat, but a long time ago I saw obesity as some odd condition where the wiring in the nervous system is not right, I truly don't think it has to do with character. And I do think our culture has gotton more and more sedentary and that is causing some people's genes to switch on and obesity is the result.

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