The yum! factor

Foods, especially sweet ones, activate the pleasure center in your brain. It makes sense for such a primal need (fuel) to be associated with pleasure. Think of it as insurance for the species: pleasure is the motivation to pursue food so you don't die.

Walt Kaye did research looking at how sugar water activated these pleasure regions in women who have recovered from anorexia. Compared to normal controls, recovered anorexics showed a blunted pleasure response to sugar water. This gives some insight on how people with AN can ignore the drive to eat- it's just not as pleasurable.

The assumption for people who are considered "overweight" or obese is that eating is extremely pleasurable, so they do it more. Aside from the assumption that overweight people intrinsically eat more than thinner people, what the found was the complete opposite. Compared to their leaner counterparts, obese women showed a lower pleasure response when they tasted a milkshake.

Says an AP story about the study:

Eating can temporarily boost dopamine levels. Previous brain scans have suggested that the obese have fewer dopamine receptors in their brains than lean people. And a particular gene version, called Taq1A1, is linked to fewer dopamine receptors...

...Brain scanning showed that a key region called the dorsal striatum — a dopamine-rich pleasure center — became active when they tasted the milkshake, but not when they tasted the comparison liquid that just mimicked saliva.

Yet that brain region was far less active in overweight people than in lean people, and in those who carry that A1 gene variant, the researchers reported. Moreover, women with that gene version were more likely to gain weight over the coming year.

Some of the other comments by the researchers were just smashingly ridiculous (such as "don't condition your brain to eat lots of Ho-Ho's"), but I think the study raises many poignant questions for people with eating disorders.

I think this study should be repeated in people who binge eat, whether they have BED or bulimia, because this could likely be eye-opening to what actually goes on inside the brain. And perhaps this blunted pleasure response to food could be part of what links anorexia to bulimia. However, says Volkow, dopamine "is not just about pleasure." Dopamine is a regulatory hormone, conditioning and training the brain, as well as helping in impulse control. Just as serotonin's functions go deeper than mood, so does dopamine's role extend far beyond pleasure.

This research forms one more piece of the puzzle, one more factor that explains why and how eating disorders start and how the brain keeps them going.

Several interesting notes:

Eric Stice, the lead researcher on the current paper, also helped with Walt Kaye's study on taste response in recovered anorexics

The different headlines from this same paper:

Brain's reaction to yummy food may predict weight (AP)
Milkshake study reveals brain's role in obesity (Reuters)
Obesity caused by deficit of brain 'pleasure centers': study (AFP)

Nice leap on the last one there, folks. Yikes. The editor who let that one pass really ought to be flogged.


mary said...

I'd be curious to know what changes occur in the brain because of anorexia. Knowing that changes are possible and senses can become dull with lack of certain nutrients, it seems like research after a disease has done it's damage may only be showing part of the story.
Also when we change a part of our diet, say give up salting food, it alters our taste buds to where a regular salted cracker becomes too salty. Same with sweets. So if we knew the inside workings of our brain BEFORE the salt or sugar was eliminated and compared we might get a truer result. Same with before and after anorexia. Then again, the thought process may have something to say about all this as well!

Carrie Arnold said...

Oh, I agree- I think we need to look at brains before AN strikes. The problem is finding those people. AN is a rare disease and so you'd have to screen several thousand people (I'm guessing) to get enough data to use.

I think I might have mentioned an interesting study where even healthy relatives of those with OCD showed changes in brain scans. I thought that was really interesting.

Anonymous said...

"Compared to normal controls, recovered anorexics showed a blunted pleasure response to sugar water. This gives some insight on how people with AN can ignore the drive to eat- it's just not as pleasurable."

That doesn't really answer any questions about the nature of eating disorders. We don't know if the blunted response was a result of damage that was done to the brain due to years of starvation. It's possible that they developed anorexia because their brains were naturally wired that way. Or perhaps their brains responded normally to sugar prior to developing anorexia and the blunted response is a result of the eating disorder.

To draw any meaningful conclusions we would have to study the responses of non-ED people and then follow them over the years to see which ones develop an eating disorder.

Anonymous said...

So yeah I basically agree with Mary.

Carrie Arnold said...

And that is one of the drawbacks of these studies- we don't know if they are an artifact of AN.

Even if we don't draw conclusions with these as to why they might have cause EDs, it certainly provides insight as to how EDs are able to propogate themselves. I mean, if recovered anorexics have less pleasure to sugar, then they probably would have during the illness as well. It might be a process with a positive feedback loop- a result of the disease *and* something that keeps it going.

I hope that makes sense.

Anonymous said...

Yeah that does make sense and that's a good point. Although the study is pretty much useless in determining the origin of EDs it does shed some light on why it's so hard to kick the disease once it has already taken hold.

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I'm a science writer, a jewelry design artist, a bookworm, a complete geek, and mom to a wonderful kitty. I am also recovering from a decade-plus battle with anorexia nervosa. I believe that complete recovery is possible, and that the first step along that path is full nutrition.

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nour·ish: (v); to sustain with food or nutriment; supply with what is necessary for life, health, and growth; to cherish, foster, keep alive; to strengthen, build up, or promote


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