Can Foods Be Addictive? Understanding The Science
While we can establish with certainty that genetics do play some role in tendencies towards gaining weight, it cannot adequately explain the global problem of obesity. While by no means the only causative factor- overeating remains the one of the main reasons for our growing waistlines. More precisely, the consumption of more calories than our bodies need from an easily accessible and readily available supply of what are termed as highly palatable foods that are high in sugar and fats. We can establish as well the idea that people who are overweight do not choose to be so, and that most conscious attempts at weight loss end in failure over the course of several months, so there must be some underlying explanation for these tendencies towards over consumption. One factor is stress and the role it plays in stimulating a significant portion of the population towards eating high fat and sugary foods (see part 1 of our series on stress and eating). The other important aspect is how such stress can bring about behaviors that are very much akin to a food addiction. Behaviors that create a self-sustaining cycle of overeating which in turn leads to a hopeless feeling of seemingly uncontrollable weight gain. We all have good days and bad days and sometimes it seems that the bad days outnumber the good ones- during these times of high stress we seek out activities and or things that bring us a sense of comfort. Some stress relief behaviors can be positive, such as balanced and mindful exercise, sports and positive relationships. However some can be negative such as gambling, substance abuse, and excessive exercise and overeating. Stress relief is indeed a two sided coin as anything that brings us that feeling of comfort can be very much destructive when taken to the extreme- but this comfort can be understood and in many cases controlled. In this article we will take a look at the reward system- that aspect of our biology that brings about the feelings of relief from stress and anxiety and explore its role in contributing to the phenomenon of addictive-like food behaviors and stress induced eating. We will also identify some of the common causes of stress induced eating- causes that ironically include dieting to lose weight! It’s a somewhat complicated subject, but by understanding how our bodies actually work it serves to bring us closer to finding viable solutions. It is my hope that these articles help shed some light on why we eat the way we do and what steps can be taken to avoid falling into or staying caught in the grips of compulsions to overeat under stress. If you find it to be of help please take the time to share it with someone who may need it.
Food Addiction: How Dieting Can Make You Overeat
It is often said that of all the hells of mythology, none are more agonizing than the ones that we sometimes create for ourselves. The self-imposed stress of stringent and restrictive dieting is one such hell. Research has borne out that the more effort you put into restricting your food intake, the more likely you are to overeat under stressful conditions.[2,3] In fact several studies have shown that those who consciously try to eat less will increase their calorie intake during times of stress as opposed to those who do not restrict their food intake at all. A group that has been found to DECREASE food intake during stressful conditions and who over all consume the same amount of calories as those who deliberately try to eat less- as their periods of overindulgence in times of stress negate any calorie reductions made during periods of dietary restriction.[4,5] Research has also shown that women who make a real effort to reduce their calories have higher cortisol concentrations than those who do not watch what they eat.[6,7,8] As we learned in the first part of our series on Stress & Weight Gain– individuals with higher levels of the stress hormone cortisol are more likely to overeat in times of stress,  with highly palatable sugary and fatty foods being the foods of choice. This phenomenon of eating more under stress when trying to reduce your calories also increases the likelihood of addictive like behavior as it strongly reinforces the idea of eating as a way of relieving anxiety.
Stress & The Reward System- How Foods Can Become ‘Addictive’
Any stressors that threaten our sense of self or create feelings of hopelessness and failure initiate a stress response involving the HPA axis. The end product of HPA axis stimulation is cortisol- a stress related hormone, which as we mentioned earlier is a powerful trigger to increase intake of high fat and sugary foods. However there is another system activated by the intake of highly palatable foods- especially under stressful conditions, and that is the reward system. The reward system is a collection of brain structures that regulates and controls behaviors by producing pleasurable effects. Pleasurable effects that compel us to continually repeat the behavior that produces it.[9,10] Activation of the reward system creates opioid, dopamine and serotonin signaling in the parts of our brain (the limbic system) that create powerful behavioral reinforcements. It is an activation of the reward system that brings about substance abuse addiction as it reinforcements the compulsion to seek and use drugs and alcohol.  While we associate activation of the reward system with alcohol and other pharmacological drugs chemical, research has shown that highly palatable foods stimulate the reward system as well [12,13], but in a different way. While drugs activate our reward pathways directly and with one main chemical being the cause of the activation, highly palatable foods do so as a result of a combination of several ingredients. Highly palatable foods also have stimulate the reward system as a result of increased glucose levels, and signals from the gut as well. It is a complex but powerful set of hormones and sensory processes that activate the reward system. when hyper palatable foods are ingested, and just as in the case of addictive drugs, repeated activation of reward pathways leads to adaptations in the brain that over time increases the compulsive desire to continue the behavior-which in this case is the compulsion to overeat. 
The Reward System- The Driving Force Behind Food Addiction
The reward system- while known mostly for its role in addictive behavior also plays a crucial role in our lives by regulating behaviors related to mating and food intake. Behaviors that under normal circumstances keep us healthy and cement our relationships. As mentioned before the reward system comprises of three signal systems- endogenous opioids, dopamine and serotonin. Endogenous, (a fancy term for something our body produces), opioids were first discovered in the 1970’s and at that time it was believed that their role was predominantly that of providing relief from physical pain.[15,16] An understandable assumption since one of the most powerful- (and most addictive) painkillers is morphine- which comes from the opioid family. However, later research showed that one role of opioids is to reinforce the behavior of ‘coming back for more’- which explains the highly addictive nature of all drugs in that class.
Now injecting mice with morphine makes them overeat- more precisely, it makes them compulsively eat foods high in fat and sugar. Highly palatable foods activate the opioid system which in turn makes the sensation of being hungry feel more intense and stimulates a desire to eat beyond what the body actually needs. But when we eat hyper palatable foods and opioid production increases, eventually those levels will taper off creating the feeling of withdrawal and anxiety associated with decreases in opioid levels. An anxiety that then compels us to alleviate it by consuming more high fat and high sugar foods. Thus creating a self-sustaining downward spiral of overeating- behaviors that many experts believe is a bonafide example of addiction.[9,10,19,20,21] While there is some controversy over the use of the term the phenomenon exists nonetheless and such overeating can result in seemingly uncontrollable weight gain.
Stress & Food Addiction: How One Causes The Other
An important point to note is that it is the taste of the food- rather than simply the fat, sugar or energy content that stimulates activation of the opioid system. Research shows that artificially sweetened foods activate the opioid system in the same way that sugary foods do [22,23,24] which partially explains the reason why the introduction of artificial sweeteners into our diets did not correspond to a reduction in obesity levels. There is another factor that sets in motion our reward system and that is stress of an emotional nature. As we discussed in the first article on stress and overeating- such stress not only activates the HPA axis but the opioid system as well. There is a great deal of research that also shows that the opioid system is our body’s way of countering the detrimental effects of emotional stress as opioid release decreases activity of the HPA axis.  Unfortunately, as we know, opioids also increases highly palatable food intake- which in turn sustains opioid release in a negative feedback loop. Eating is thus a powerful tool for shutting down HPA axis activation and use of high sugar and high fat foods has long been described as a method by which many individuals ‘self-medicate’ as a form of stress relief.[27,28] However, if stress is chronic and there is a learned response of using food as a coping mechanism the stage is set for the consumption of highly palatable foods as an ‘addictive’ behavior.
Two other neurotransmitters are involved in activation of the reward system- dopamine and serotonin. Dopamine pathways have an effect on eating behavior by increasing arousal and food seeking. Injections of dopamine and opiates have been shown to increase intake of sugary and fatty foods- while serotonin has been shown to control satiety and the feeling of well being. It has a powerful effect on mood elevation and as such it is no surprise that most anti-depressants work by ensuring higher levels of this neurotransmitter. Serotonin has also been shown to have some effect on food satiety and like opioids, serotonin also plays a role in the relief of stress.  Consumption of carbohydrates has been shown to increase serotonin turnover- which explains why individuals suffering from depression often turn to high carbohydrate foods as a coping mechanism to increase well-being.
The Role Of Intermittent Fasting & Food Restriction In The Development of Food Addiction
While stress is a strong factor in the development of addictive behaviors towards food, another powerful factor is the nutritional state of the individual. Studies show that intermittent fasting increases the not only the rewarding effect of foods- but of chemically addictive drugs as well. [34,35,36,37] (See my article on Intermittent Fasting – A Bad Idea For Weight Loss) The popular weight loss methodology of restricting calories during the week and then indulging in ‘cheat meals’ of high fat or high sugar foods not only provokes binge eating, but significantly activates the reward system- setting up a scenario for overeating and food dependence further down the line when the diet is over. As we mentioned earlier, the stress of food restriction has been shown to increase intake of highly palatable foods and thus it is important to understand the dangers of any extreme dietary measures. The hard dieting and restrictions with or without cheat meals may work to temporarily reduce body fat- but in the long term, like intermittent fasting- it does not nurture healthy eating habits- if anything the increased potential for food dependence and bingeing at the inevitable end of the diet can not only undo the progress made- but set the stage for continued overeating.
The Real Origins Of Food Addiction- Modern Foods Designed To Make You Eat More
Without the introduction of modern, multi-ingredient highly palatable foods into the human diet, addictive food behaviors do not occur. It is important to keep in mind that we have been eating one ingredient foods and foods with minimal or no processing for the past several hundred thousand years of our existence on the planet. During this time terms like obesity and metabolic syndrome did not exist- nor did the possibility of food addiction. With the advent of modern processed foods designed to make you eat more over the past hundred years or so -the problem of food dependence develops. A circumstance that is immensely profitable for the food industry (See my article on Why the Food Industry Needs Us to Overeat). Foods in their natural form generate information on its calorie content and taste in our brains- signals that are transmitted to the hypothalamus which then releases or up regulates various peptides that make us feel full and satisfied.  It is a system of near perfect balance that has evolved as we have to keep us healthy and maintain our body weight and food consumption within optimal levels. Modern processed foods however, react very differently in our bodies because unlike natural foods- we haven’t had the benefit of 2.4 million years to adapt to them in a way that we can consume them and maintain optimum health. With highly palatable foods, there are several multiple ingredients in addition to being high fat or high in sugars- combinations that would not be found in nature and thus our body does not react well to them. Taste sensation is far more intense when they are consumed and information is sent to the reward centers of our brain- leading to the release or up-regulation of opioids dopamine and serotonin- which instead of triggering the commands to stop- does the opposite and makes you consume more than you should.
Our problem today is that food manufacturers are not only aware of the addictive nature of many of the foods they make- but in fact they develop foods with test groups so as to ensure that they are indeed as habit forming as possible. It isn’t an unfortunate coincidence- but well researched and carefully planned ingredient selection combined with ever present marketing and powerful lobbying at the highest levels to ensure that these foods are never maligned. One of the simplest nutritional pieces of advice any health care provider could give would be to avoid highly processed foods. Yet even the notion of eating less of them is one that you will not hear in the public sphere because of the influence of the industry itself.
So how do you avoid such food dependent behaviors? Some experts advocate the use of opiate blocking drugs such as a naloxone as a way of breaking the chemical dependency of high fat and sugary foods for relief of anxiety and as a tool against obesity. A simpler and more practical solution however would be avoidance of highly processed foods in the first place. This solution is a difficult one, however as we are forever burdened by an onslaught of processed foods- so much so that in many urban parts of the developed world, finding simple, natural foods can be quite a task. The food industry sees to it as well that processed foods are not labeled as potentially bad for your health and spend millions in lobbies to see to it that this does not happen on a large scale. The very notion of food addiction is challenged mainly by the food industry as if certain foods were labeled as being potentially addictive it would require regulation - regulation that would cut tremendously into their ability to turn a profit- and so much of the research regarding the addictive like qualities of high sugar and high fat processed foods never makes it to the mainstream consciousness.
That being said, it is not impossible to avoid processed foods and other more positive coping mechanisms for stress relief have to be found- such as exercise or other forms of activity. Care must be taken that those actions do not lead to addictive type behaviors as well since exercise addiction is very real and many individuals with food compulsions gravitate towards exercise in the same way. In the end the idea is finding a balance between eating well with natural and non-processed foods along with healthy and wholesome approaches to exercise as a way of life. One that helps us do our best to deal with the ever present stresses that everyday life can bring.
Be sure to read part 1 of our series: Can Stress Make You Overweight? Understanding The Science
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