Obesity is a growing problem for our country here in America. But eating may actually have the ability to trigger our reward system and make us more likely to want to eat more and become less likely to stop when we feel full. The foods that we consume in our diet can also have a great effect on the systems and biochemical pathways in our bodies. Foods high in fat in sugar can actually cause food addiction in some people. One of the pathways in our bodies that can be affected by our diet is our endocannabinoid system.
The endocannabinoid system and the reward system
Endocannabinoids are produced from arachidonic acid as a precursor. The two endocannabinoids that are most extensively studied are N-arachidonoylethanolamine (anandamide, AEA) and 2-arachidonoylglycerol (2-AG).
The binding of these eCBs to cannabinoid receptor CB1 (yes, the same one that THC from the cannabis plant binds to) can affect the release of several neurotransmitters in the body, but especially glutamate, GABA, and dopamine. Glutamate is the main excitatory neurotransmitter, meaning that it will cause cells to become activated, release hormones, and carry out functions, along with other things. GABA is the main inhibitory neurotransmitter, so it keeps these processes from happening. Dopamine is the neurotransmitter involved in the reward system that gives you that “feel good” feeling when it is released.
In normal resting state, GABA is inhibiting dopaminergic neurons from releasing dopamine. When THC and eCBs bind to the CB1 receptor, it inhibits GABA neurons, so this stops the inhibitory effect GABA is having on the dopaminergic neurons. This results in the release of dopamine as those neurons are not being inhibited any longer, leading to satisfaction and the reward sensation.
Food and the endocannabinoid system
It has been found that some foods can activate this system as well, which may be contributing to this problem of obesity. When high fat diets are consumed, it is putting more fatty acids in the body, which leads to the precursors for the production of some of these eCBs. Thus, eating fatty foods can trigger this reward system, making you feel good when you eat it, and you want to eat more. Because food is so available everywhere in our country for most people, it become so much easier to fall into this pattern of eating too much, especially of unhealthy foods.
It has also been found that there can be some differences in the expression of these CB1 receptors in people who suffer from obesity. An example of this is that they may under-express these receptors, and thus they need to eat more food in order to feel the same amount of satisfaction, because they are not getting the same amount of dopamine released eating a normal amount of food. In obese people, it has also been found that they may have lower levels of some of the enzymes that break down fats, which keeps more eCBs around to trigger the reward system. This leads to consuming more food than is necessary as continuing to eat can make them feel good.
The future of obesity
This leads to the question of things that we can try to do to help control the growing number of cases of obesity. As it has been seen that there is an upregulation of the eCB system or the overproduction of eCBs in people struggling with obesity, one option that is currently being researched would be using CB1 antagonists to try to quiet the system down and not cause the urge to eat as much. This may also be key in preventing some other prevalent diseases in our society such as cardiovascular and heart disease and diabetes type II.
How the Reward System Contributes to Obesity
