Here I am again, writing about food, obesity, and the brain. This article really was about obesity though, and it’s not that surprising that when there has been an connection to weight I have taken the opportunity to write about it in my blog, because like so many Americans I feel like I am constantly thinking about food. The central role of food in our society is undeniable. Holidays, dates, life in general is planned around food. How to get closer to your kids? Eat dinner with them. Food is often used as a reward for good deeds, good grades, even potty training.
Why is this such a big deal? Well, there are a couple of different parts of the brain that are particularly associated with food: the part that tells you when you are hungry or full, and the part that feels the reward, how good a food tastes, etc. Leptin and insulin have been found to play a crucial role in the first part, maintaining food intake homeostasis, making sure that the body receives the appropriate nutrients, and maintaining energy expenditure. At the most basic level, how this works is that leptin and insulin work on the NPY/AGRP and POMC neurons. When there are decreased levels of insulin and leptin it stimulates the NPY/AGRP neuron which in turn stimulates food intake. Decreased levels of insulin and leptin stimulate the POMC neurons, giving your brain the signal that your body is full. Neat stuff, really!
When you enjoy eating food is stimulates the dopaminergic neurons which are associated with reward. This can become a learned behavior when food is used as a reinforcement for a good, or a positive reinforcement which would imply that the consequence increases the frequency of a behavior or maintains the frequency. A child who is rewarded with candy for finishing their homework may get to later years in their education and find that they want candy to do any homework at all. There have been studies that think that food reinforcement may be important to obesity studies (http://www.ncbi.nlm.nih.gov/pubmed/17907820). Food reinforcement for one good behavior may turn into reinforcement for multiple behaviors and turn into eating often, even when not hungry. Does anyone else ever feel like they can reward themselves for a good workout by eating something they know they shouldn’t eat, like a second piece of cake, or go out to eat for no good reason when you have plenty of delicious things to eat in the fridge? That is an example of learned behavior and using food as a positive reinforcement. So is this a part of what is leading to obesity in America, overeating, emotional eating? Just a few thoughts.