Dopamine signalling findings: Support for a physiological theory of disordered eating and motivation to keep on keepin’ on
Today I woke up to a really awesome, generous surprise in my inbox. One of my best friends, we’ll call him Dan, recently attended a lecture by Frank Guido, a neuroscientist at the University at Denver. Dan took great notes, and he took enormously gracious initiative to type them up and send them to me. And now I am going to pass them along to you. Unfortunately, I don’t have the details of any of Guido’s studies. All I’ve got are the take-aways. So I’m going to put a little bit of faith in Guido’s science (epistemologists say science is a faith anyway) and allow this awesome gift to inform my life and methods.
Guido’s talk focused on dopamine level comparisons between anorexic, bulimic, and obese patients. Recall that dopamine is a pleasure hormone, stimulated by the act of fulfilling survival needs. This is (partly) why we eat, and (partly) why we have sex, and all of those other very basic, very human, very animal things. One thing that’s both fascinating and important to note is that dopamine, while pleasurable, is associated primarily with survival, and not with pleasure. Therefore, with dopamine signalling, our bodies are trying to make us “healthy.” They are doing what they can with the resources they have available. They don’t want to make us have fun. They want to fix us. This, in my humble and highly uninformed opinion, supports the “set point” theory of weight loss. Your body, for one reason or another, has a certain idea of what your “correct” body size is, and will adjust your dopamine regulation accordingly. So what do you do with this information? Maybe that means you want to allow yourself to put on a few pounds. It could help you feel more satisfied. Or maybe it means you can now more easily forgive yourself for your cravings. Or perhaps you want to buckle down and fight anyway. It’s your body, and your decision.
Anyway, first, Guido notes that Anorexic subjects generally have high dopamine levels in their cerebral spinal fluid. This is because anorexic subjects “are good at delaying rewards,” and “have an elevated drive to avoid harm.” Bulimic
subjects, on the other hand, have low dopamine levels in their cerebral spinal fluid. This, according to Guido, correlates to bulimic subjects being “impulsive,” and “having reduced inhibition.” Third, obese subjects experience lower and lower dopamine receptors the higher their BMI. This suggests that our bodies give us less and less reward for eating if we are overweight. This makes sense. Also, according to Guido, obese subjects ” are also impulsive and poor inhibitors.”
Then Guido discusses his experiment. In an fMRI, researchers measured dopamine responses to sweet flavors.
This is what they found:
Anorexia nervosa patients experience an increased dopamine response to sweet flavors. We can infer from this information that anorexic patients are hypersensitive to self-harm (i.e. weight change). Their bodies give them high amounts of satiation for eating. That’s quite enough!, says the sensitive patient.
Binge eating and obese patients have decreased dopamine responses to sweet flavors. This means that they need more stimulation to feel satisfied. Binge eaters have developed a “food tolerance,” — much like we discussed before, with drug habituation. (Read: Food addiction: harder to kick than cocaine?) Moreover, the more frequently someone binged, the more dopamine they required to feel satisfaction.
Yikes. So what do we conclude?
The more frequently someone binges, the lower his dopamine response. Guido also notes that the more (calorie) restricted he is, the lower his dopamine response. These facts mean that:
1) If you severely calorie restrict or under-eat in any fashion, or are underweight according to your “set point,” your body is going to try to get you to eat more. It will require you to eat more food to feel satisfied. It will do this until you ingest the “proper” amount of calories or until you reach the “proper” weight. Therefore, it is not necessarily your fault if you feel so restricted and so unsatisfied. Your body might be veritably begging you to eat.
2) Your body gives you less and less reward the more and more you binge. This is because it is habituated to the behavior. So what do you do about it? You should binge less. I KNOW! CRAZY IDEA! The thing is: this motivates me to reach for food less often. It helps me stop. Because if I don’t binge now, it’s going to make my life easier later. And how nice would that be? Every single time I refuse food it is going to get easier and easier to refuse, and my body will get more and more adjusted to my new eating habits. I will begin to feel more satisfaction from a normal diet, and I won’t have to eat so much to feel satisfied. Just like my body got conditioned to eating way too much, I can recondition my body to eat the proper amount of food. All it takes is a first step, and as much diligence as I can muster throughout.
So keep on keepin’ on! Each time you do a good food behavior you are making it easier to do it the next time. If that’s not motivation, I don’t know what is. For real.