The Science behind Food Addiction – The Brains Behind The Binge
We have heard it many times – ‘Oh, I am addicted to chocolate’ or ‘I cannot stop eating these sweets!’ Food addiction is now all too common, and is a well recognised scientific fact that is still being extensively studied primarily to understand obesity.1 While the entire concept does appear simple, it does in fact involve a complex interplay between neurochemical mediators, neuroanatomical pathways and learning mechanisms. In some cases, food addiction has been classed in a similar category to drug addiction within the Diagnostic and Statistical Manual of Mental Disorders (DSM – IV) as ‘dependence’. 2
In this article, we will briefly discuss food addiction, concentrating primarily on the different changes in the brain associated with food addiction as we understand them today.
The topic of food addiction still is a mystery. One of the questions that still remains unanswered and unclear to this day is ‘what is addiction?’. Why is it that some foods are enjoyed more while some not so much? After all, we all need food to sustain life, and whether addiction to certain foods and dislike of the others has an impact on our lives it still unclear.
It also is a mystery as to why it is that the foods we are addicted to tend to be high fat or high sugar containing foods. This also leads to the question – when does consumption of a food item reach a point where it is addictive rather than just being one that a person really enjoys? Using the DSM-IV criteria for dependence may not necessarily work unless foods that people are addicted to are classed as ‘substances’ and the addiction to food is classed as substance abuse.
Clearly, there is still plenty of research that still needs to be conducted, and hopefully one day these unanswered questions will have an answer that is backed by scientific proof and evidence.
If we are to compare food addiction to drug addiction based on the DSM – IV criteria, then there has to be evidence of food withdrawal symptoms or changes and evidence of development of tolerance. What this would mean is that within the brain, changes will need to occur that are consistent with developing tolerance and withdrawal. But this may not be enough by itself.
It is worth recognising that in drug addicts, attempts to stop the drug usually fail, and this forms a criterion in defining addiction. If such a phenomenon occurs with food as well, then it may be considered that the person is addicted to food. However, this is rarely seen, which again raises the question of whether food addiction in fact exists.
Neuro-chemicals and food addiction
Our brain functions at optimal capacity and controls a number of different processes throughout the body by releasing a variety of chemicals within it. Most studies that have been performed to study addiction have involved animals rather than humans. In many cases, food addiction has been compared to drug addiction. In cases of drug addiction, it is well known that what once starts as an ‘experiment’ or a ‘bit of fun’ can turn into a nasty addiction that can take over a person’s life.
In cases of drug addiction, the initial stages of the addiction stage where the person is just trying the drug has shown to invoke responses that are under control of the prefrontal and ventral striatal aspect of the brain. Over time however, this can become controlled by the dorsal striatum which in fact results in a loss of control and drug seeking behaviour.3
Areas that are connected to this dorsal striatum such as the prefrontal cortex also stimulate compulsive behaviour and decrease the ability of the person to control their craving for the drugs.4 It is believed, though not completely proven yet, that food addiction bears a similar mechanism of development to drug addiction.
If one were to take a closer look at the chemicals released, similarities can once again be found between food addiction and drug addiction. Dopamine is considered to play a primary role in drug abuse, and the same is considered in people who develop food addictions. It plays a key role in the reward system that regulates appetite and behaviour. However, studies have shown that the dopamine reward system is less sensitive in obese individuals.5 This would mean that more of the pleasurable foods need to be ingested to adequately stimulate the reward system and provide the person some satisfaction. Whether or not this is exactly how the mechanism operates however is still not clear.
There is some evidence that does demonstrate similarities between withdrawal from pleasurable, addictive foods and drug withdrawal. Work by Lutter et al has shown that the signals seen in the brain of people who stop consuming high fat diets are similar to those of people withdrawing from drugs.6 This could imply a similar mechanism in the pathogenesis of food addiction and drug addiction.
Other than dopamine, there is some evidence suggesting that blockade of opioid receptors in the brain can reduce the intake of food. It is believed that the release of opioids within the brain can stimulate the production of dopamine, which in turn stimulates the reward system. While this could imply that opioid receptors play a role in food addiction, blockage of these receptors does not seem to have any effect on hunger, but only seems to affect the feeling of satisfaction one has after the intake of ‘addictive’ foods.7
From the above discussion, it is evident that there are changes that occur within the brain that could be considered to be consistent with being addicted to food. However, with the lack of specific criteria to diagnose food addiction, one can only assume that this condition exists. Research still needs to be conducted in humans that will identify specific parameters to help define this rather difficult topic.
1. Volkow ND, Wang GJ, Tomasi D, Baler RD. Obesity and addiction: neurobiological overlaps. Obes Rev. 2012
2. American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders – DSM-IV-TR, 4th Edn. Washington, DC: American Psychiatric Association.
3. Everitt BJ, Belin D, Economidou D, Pelloux Y, Dalley JW, Review RTW. Neural mechanisms underlying the vulnerability to develop compulsive drug-seeking habits and addiction. Philos Trans R Soc Lond B Biol Sci. 2008;363:3125–3135
4. Koob GF, VolkowND. Neurocircuitry of addiction. Neuropsychopharmacology. 2009;35:217–238.
5. Wang GJ, Volkow ND, Logan J, Pappas NR, Wong CT, Zhu W, Netusil N, Fowler JS. Brain dopamine and obesity. Lancet. 2001;357:354–7.
6. Lutter M, Nestler EJ. Homeostatic and hedonic signals interact in the regulation of food intake. J Nutr 2009;139:629–32
7. Yeomans MR, Gray RW. Effects of naltrexone on food intake and changes in subjective appetite after eating: evidence for opioid involvement in the appetizer effect. Physiol Behav. 1997;62:15–21.