One rarely sees an animal on the plains of Africa which is obese. Three hundred million years of evolution has resulted in the creation of many biochemical processes to ensure that animals maintain an ideal weight so they can pass on their DNA to the next generation.
The processes which determine how much food we eat is primarily controlled by our subcortical brain which is located in the middle and lower part of our brain and it controls many bodily functions and instincts like hunger, reproduction and caring for our young. Located above the subcortical brain is our cerebral cortex. Humans have a very large cerebral cortex and it is where we make decisions like should I exercise today? and should I call my mother today? (Answer: Yes and yes.)
Typical post-dinner scenario:
A few hours after dinner, even though you are not really hungry, you open the refrigerator and see a food you like. You then have a conversation in your mind that goes like this:
Subcortical brain: That cookie looks good, let’s eat it.
Cerebral cortex: Do not taste it, you know if you taste it you will then eat the entire box of cookies.
Subcortical brain: No, I will only have one cookie.
Cerebral cortex: You will not eat only one, you will eat it all.
Subcortical brain: No, this time I will control myself and only have one.
Cerebral cortex: Noooo, DO NOT EAT IT!
Subcortical brain: I promise, this time it will only be one.
Cerebral cortex: You promise, only one?
Subcortical brain: Yes, only one.
Cerebral cortex: OK, only one.
You eat one cookie and the various reward centers of the brain are stimulated by the chemicals in the cookie.
The entire brain: Wow, that was really good!
Subcortical brain: I want another cookie!
The eating continues until the cookies are completely consumed.
Cerebral cortex: Damn, why did I do that again?!!!
The subcortical brain controls our instincts, it is more fundamental to the functioning of life and frequently wins when there is a conflict with the cerebral cortex. While we like to believe we are rational beings, to some extent, our subcortical brain controls our behavior.
When the subcortical brain evolved, food was hard to obtain and starvation was a real danger. In order to reduce the risk of starvation the subcortical brain developed many mechanisms to ensure that the animal maintained an ideal weight.
Based on a recent study, it appears that when people and animals eat ultra processed foods (like sweet, fatty or salty packaged snack products, ice cream, sugar-sweetened beverages, chocolates, confectionery, French fries, burgers, hot dogs, poultry and fish nuggets) a chemical(s) in (or missing from) these ultra processed foods alter the function of our subcortical brain and tell us to “keep eating.”
So now, once we start eating the cookie, the subcortical brain issues its “keep eating” command and even though our cerebral cortex tells us to stop eating, we overeat and gain weight. The same process occurs in wild animals who eat ultra processed foods, like city rats, who also become obese.
We must acknowledge that our eating behavior is influenced by commands originating in our subcortical brain and while we have “will power” it is not the only factor which controls our behavior. As we cannot alter how our subcortical brain responds to the chemicals in ultra processed foods, we need a solution to prevent our subcortical brain from issuing the “keep eating!” command.
One solution is to use our cerebral cortex (the thinking part of our brain) to outfox our subcortical brain. You can do this by removing all the ultra processed foods from our home. Without the stimulus from the ultra processed foods, the subcortical brain will never issue the “keep eating” command.
So, before you next go food shopping, first eat lunch. Then make sure you do not bring home those ultra processed foods that cause your subcortical brain to issue the “keep eating” command. Your cerebral cortex and your entire body will thank you. And your subcortical brain will be fine.
An experiment you can try at home:
After you have dinner and before you sit down to watch TV, put 5 small bags of potato chips in front of you. Each bag of potato chips will have about 150-250 calories, look on the label for the actually calories per bag. At the end of the evening, determine how many potato chip calories you ate.
On the following evening, put 5 apples in front of you. Each apple contains about 100 calories. At the end of the evening, determine how many apple calories you ate.
Did you eat more potato chip calories or apple calories?
Hayward Zwerling, M.D.