Today I will be talking about the common reward pathways that food and drugs affect in the brain.
Obesity is considered a multi-faceted and complex disorder that is the result of a combination of genes, metabolism, hormones, overeating, lifestyle and environment. We in the west live in a world where tasty and cheap food is abundant and where we can buy rewarding sweets pretty much everywhere. The effect of this is that many of us are constantly battling urges to succumb to our sweet tooth or downing down that greasy (and deliciously tasty-looking) burger on the fast food-ad.
The notion that food can be an down right addiction is perhaps controversial to some, and there has been alot of debate in medical journals and in general literature. The term ”addiction” has traditionally been applied solely to the use of drugs that activate the brains reward pathways in the mesolimbic region. More recently so called ”behavioral addiction” has been incorporated under the umbrella of addiction. It seems that all kinds of addiction share the similar reward pathways; whether it’s food, gambling, sex- or cocaine addiction. Recent scientific findings further support the theory of food addiction, describing how food affects our neurochemistry through dopamine, endogenous opioids, endocannabinoids, the limbic pathways, and self-medicating behaviors.
The foods that seem to have the most addictive properties include carbohydrates, sweets and fats, processed and highly salty food. This form of food addiction may represent a phenotype of obesity. Periods of internal and/or external stress might predispose vulnerable individuals to use food as a means of self-medication.
There are different schools of thoughts that approach things differently, however; There is the sugar addiction model, that tells us that sugar causes addict-like behavior in humans, affecting reward pathways etc. However the literature is a bit inconclusive. There is also the evolutionary theory, saying that high-reward food (which tends to be high in calories), might be an adaptive survival strategy in an environment where food is scarce. This is obviously not the case in our modern society, which is where our nature and society presumably collide. Maybe these two facets don’t have to be mutually exclusive.
When we seek out high caloric foods we engage our rewarding mesolimbic pathways which in turn reinforces our addictive behaviors. This has been shown in imaging studies where different parts of the brain are activated by both food and drugs. Both cause the release of dopamine in the brain, which is a neurotransmitter that plays a major part of our brain reward system. In the reward model for food addiction, the expected reward overactivates the pathways for reward and motivation while at the same time inhibiting the cognitive control circuits, which results in a functional inability to inhibit the drive to consume the food despite attempts to do so.
Beside our innate preference for rewarding food, the fact that these foods also are legal, accessible and relatively cheap can exploit vulnerable individuals likelihood of having issues with food. However, not everyone becomes hooked on to a drug, and not everyone becomes addicted to eating high-calorie foods. Both genetic predispositions and changes in the brain after excessive use over time, specifically downregulation of D2-receptors determine the probability of addiction.
Personality traits also play a role in addiction and obese individuals tend to be more impulsive and sensitive to reward and punishment. The reason these people overeat compulsively go beyond mere sensations of hunger, and is psychologically rooted. High-calorie rewarding foods may produce feelings of pleasure and reduce pain just like drugs do. Research shows that ”emotional eating” is a response to reduce negative emotional states such as boredom, anxiety and depression.
There is however a debate on whether obesity should be associated with addiction. A big reason is that there probably is a difference between food and drugs because of the gut-and fat derived hormones that work as a peripheral signaling system in food intake. Neuropeptides such as PPY, CCK, hormones such as leptin and insulin all play a role in obesity. Obesity is presumbably more complex than being a state of downright addiction, while addictive behaviors apparently do have a real part in it. However, humans have a ”free will” and cognitive processes can override experienced wants and needs to a certain degree.
There is also the fact that addictions can change their face, which for example is seen sometimes in obese individuals following a gastric bypass, where they for instance take up gambling instead. A person might also start exercising and becoming addicted to running, which might negate or lessen the negative effect that food has in terms of weight gain and the actual addictive part of food which is switched out for an ”addiction” to exercise.
To sum this up, I am gonna discuss some strategies that might help a person to break their addiction-like behavior in regards to food. First of all I think adopting an exercise plan of some sort is very important and marks a step towards a healthier lifestyle. Healthier does not mean boring by the way – just to be clear about this. There is also the fact that exercise of any sort uses up calories, has insulin-sensitizing effects and generally tends to improve our body composition. Which is always a good thing. So if you exercise, you can eat more without gaining body fat and the food you eat will be used as fuel by muscle preferrably.
Second, I think a person with food issues might want to take up a low-reward food plan. I have been reading alot on the subject lately and I’m probably gonna do a write-up on this soon, but in short form one theory goes (which is supported by what I’ve written above) that low-reward food induces weight gain and makes loosing weight less of a chore than just cutting down portions of high-caloric foods. In practical terms that means reducing salt intake, sugar, large amounts of fat, spices and everything else that makes food more appealing.
The mindset should change to that of food being fuel first and foremost, which actually is true. Eating rice, with chicken breast and broccoli is not especially rewarding but it can be a pretty nice meal still and will make you full. You will probably not crave it, which makes it not a likely candidate to gorge on. Also my anecdotal experience is that consuming sugar definately makes you inclined towards consuming more of it, so stripping away sugar from your food and possibly reducing starch somewhat can make you crave sweets less.
That’s all for now.
Obesity and addiction– http://ajp.psychiatryonline.org/data/Journals/AJP/4237/ResidentsJournal.pdf
The obesity epidemic: the role of addiction – http://www.cmaj.ca/content/182/4/327.full
Food addiction: true or false? – http://www.ncbi.nlm.nih.gov/pubmed/20042860
Overlapping neuronal circuits in addiction and obesity: evidence of systems pathology – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2607335/
Eating disorders, obesity and
addiction – http://onlinelibrary.wiley.com/doi/10.1002/erv.1048/abstract