Elizabeth Cohen: New study links obesity to brain receptors

CNN Medical Correspondent Elizabeth Cohen reports on a study relating obesity to the amount of dopamine receptors a person has.

CNN Moderator: What factors make some people more prone to obesity?

Elizabeth Cohen: That's the $64 million question. There are so many factors. Doctors are just beginning to understand them all. There are physiological factors, psychological factors and genetic factors.

What this new study seems to say is that obese people don't have the normal amount of dopamine receptors in their brains. Dopamine is a neurotransmitter responsible for feelings of pleasure and satisfaction. If you don't have enough receptors, you won't feel those feelings as much as other people. The researchers did PET scans to image the brain to notice a deficiency of dopamine receptors in those who are obese. Addicts and alcoholics, by the way, also have the same deficiency. So it's thought that people overeat, do drugs and drink too much for some of the same reasons.

MESSAGE BOARD Health   ALSO Link found between obesity and brain receptors

CNN Moderator: What do researchers recommend to correct the dopamine imbalance or work around it?

Elizabeth Cohen: Right now, the only thing you can do is exercise. That seems to help increase the level of pleasure/satisfaction feelings There are also amphetamines, prescription drugs that work on dopamine. But many doctors are hesitant to prescribe them because they're so addictive.

Question from chat room: Can we infer that slim people have more receptors than the average person?

Elizabeth Cohen: Interesting thought. They didn't do PET scans of especially thin people -- just obese and "normal" weight people. But that's an interesting theory.

Dopamine is one of many neurotransmitters. The important thing to remember, in the context of this study, is that it doesn't seem to matter much how much dopamine you have -- you could be swimming in it -- but if the receptors in your brain can't "receive" it, you won't feel the kind of pleasure and satisfaction that you otherwise would have.

Question from chat room: How will these findings affect the way people are treated for obesity, and does this help explain why dieting often fails?

Elizabeth Cohen: Right now, it won't really change much. It's just more evidence that lets doctors know that obesity is a disease, not a character flaw. And yes, this could explain why dieting often fails. If your body is having a hard time feeling the usual satisfaction and pleasure that other people get from eating, you could very well have a hard time dieting.

Question from chat room: Could this also explain why many obese people report eating to fulfil emotional feelings such as happiness or overcoming stress?

Elizabeth Cohen: Yes, exactly. So when people say obese people eat for "emotional reasons," in a way they're right. But this study shows there may be a biological underpinning for those emotional reasons.

Question from chat room: Can more receptors be "grown" or produced by weight modification?

Elizabeth Cohen: It's interesting, because doctors say this receptor/weight relationship is like the chicken and the egg. They don't know which comes first -- do overweight people have fewer receptors to begin with and that's why they overeat, or does their overeating cause the decrease in receptors. So your question is exactly the type they'll be looking at next. Can you "grow" more receptors by gaining weight, losing weight, developing new drugs, etc.

CNN Moderator: Do you have any final thoughts to share with us today?

Elizabeth Cohen: This is just one more study that shows, as one expert put it to me, "obesity is not gluttony." There is a whole movement among scientists to make people realize that obesity is a disease with real physiological causes. Research into the hormones leptin and insulin point in this direction also. It's probably going to be a while before drugs are available that would act on dopamine, leptin, or insulin, but that's where science is headed.

CNN Moderator: Thank you for joining us today

Elizabeth Cohen: Good-bye and join our health chat next week!

Check out the CNN Chat calendar
Post your opinion on our message boards