Drug of Choice: Food
Weight loss is always a popular topic of New Year’s resolutions, talk shows and self help guides. However, recently concern has turned toward a more severe form of weigh gain, obesity. It seems one cannot open a newspaper without reading about it. In fact, in 2000, Philadelphia was the fattest city in the United States and in 2005 the third fattest city. (1) Clearly, obesity is a pervasive problem, a disease occurring with alarming frequency. Being obese, having a body mass index of over 30, (2) is associated with risk factors such as high blood pressure, coronary artery disease, sleep apnea, cancer, diabetes, and death: 300,000 deaths a year in the United States are linked to obesity. (3) In 1998, the Nation Institute of Health (NIH) found that 55% of the United States population is overweight, and estimated that in 2004 this had climbed to two-thirds of adults in the US. These statistics have grabbed the attention of both the NIH and the World Health Organization (WHO), which composed a Global Strategy on Diet, Physical Activity, and Health in 2004. (4) While many factors and causes are being investigated for this growing problem, the science behind addiction can help us understand this disease.
There are three main factors that go into any addiction: genetic, environmental, and neurobiological. (5) Under the conditions of specific studies, “40-60% of the vulnerability to addiction and 50-70% of the variability in body mass index might be attributed to genetic differences.” (5) Although this is an extreme example, and only specific to this particular study, it does show a valid point; that genetics does play a role in obesity and addiction to food. Studies have found that certain point mutations in a gene sequence can play a vital role in obesity and addiction. However, more specifically, these genes are under polygenic control. This means that a certain combination genotype may make a person at higher risk for obesity or addictive behaviors within specific genders or in the presence of particular environmental cues. (5)
The largest environmental factor that accounts for obesity is the high availability and volume of foods heavy in carbohydrates, fats and sugars. These foods are usually packaged as snack foods, easy to eat in today’s hectic environment and their contents are addicting. These types of food are also cheaper than their healthier counterparts. These foods are particularly dangerous to children as they are marketed toward their age group, readily available at school and start the addictive eating behaviors associated with obesity at a young age. Foods high in sugar and carbohydrates are associated with quick energy burst, and were beneficial to early man who lived in an environment where food was scarce. However, the genes that were favored under these times are no longer beneficial to man in an age where more high fat food is consumed and less exercise is done. (5) A second important environmental factor is stress. Both long term and short term stressors can encourage the use of excessive food and drugs. The corticotrophin-releasing factor (CRF) controls the pituitary-adrenal axis, and mediates stress controlling the central effects. CRF is also involved in the food intake and energy regulation. It has been implicated in the stress indicated relapse of drug addiction, and is being investigated for its role in contributing to food addiction and obesity.
The closest similarities between food and drug addiction lie in the brain’s neural structures and hormones. Leptin is a hormone secreted by adipose tissues (fat) that possesses the ability to block additional eating. Leptin is released by fat tissues and travels through the blood stream to the hypothalamus where it suppresses hunger. It has been postulated that perhaps obesity occurs as a problem with this feedback mechanism, impairing the suppressive action of leptin. Interestingly, leptin has recently been implicated in addictive behaviors as well. The hypothalamus, which regulates eating behaviors, is also controlled by the nucleus accumbens. The nucleus accumbens is a bundle of nerve fibers that acts as a rewards system and runs from the mid brain. These structure secrets large amounts of dopamine when an individual sees something that is pleasurable, such as food. In 2001 Gene-Jack Wang found that the amount of dopamine receptors closely correlated with BMI, the higher the BMI the fewer the reward receptors. (3) Similar findings are found in the brain of drug addicts, a lack in the number of dopamine receptors. Drug addicts and obese individuals alike must seek external rewards in order to compensate for their lack of dopamine receptors, whether through food or drug. However, the brain compensates for this by down regulating the small number of dopamine receptors that exist, further compounding the problem. (3)
Two other brain regions associated with drug and food addition are the amygdala and the orbitofrontal cortex (OFC). The amygdala contributes to modulation of satiety, but also acts as an alarm system to the body. When food is seen by a hungry individual, this area of the brain becomes highly active, the same occurs with drug addicts. However, once the person is full or injects the drug this area turns off. The OFC is involved in addiction and is located just behind the orbits of the eyes. This area controls and monitors many of our behaviors. Similar, to the amygdala when an individual is enjoying food (or some pleasure) this area is active; however once they are satiated it turns off. (3) A final aspect of drug and food addiction is simply the behavioral patterns of abuse and use.
There are many areas in the brain that are associated with both drug and food addiction, however these two vices are very different across many levels. Individuals who are addicted to food do not sufferer withdrawal in the same biological and physiological manner as drug addicts, however, they do suffer a strong dependency to the extent that they withdrawal from and neglect other areas of their life. It is important to understand the connection between food and drug addiction as it opens many alternative treatment alternatives.
Naltrexone, typically used with cocaine addicts, is an opiate antagonist that blocks the pleasure that is experienced with drugs. These opiates are also active when an individual receives pleasure upon ingesting “palatable food.” (5) With the help of drugs such as naltrexone and rimonabant (an endogenous cannabinoid system antagonist) individuals have lost weight (note: Naltrexone is reportedly more helpful). (3) An herbal rememdy for this problem, especially addiction to sweets, is Sugarest, an all natural herbal remedy that blocks the sweet receptors on the tongue. This product reportedly guarantees that the individual who has taken the pill will be unable to taste sweetness for thirty minutes to an hour. The product further claims that the individual will “lose [their] cravings and desire for sweet fattening foods… [resulting in] healthier eating habits and a new slimmer you.” (6)
When it comes to treating and preventing obesity, there is one huge difference from drug addiction treatment. Food is necessary to human survival and food withdrawal or abstinence cannot be achieved in the same manner as drug withdrawal or abstinence. Due to the many factors of food abuse in obesity, a multilevel treatment plan needs to be implemented. This includes incentives, motivation, cognitive behavioral therapy, 12 step programs, diet modification and exercise. (5)
Obesity is currently viewed as a “behavioral problem” in our society. Greater consideration of biological addictive factors must be considered if we are to effectively treat obesity. Being an obese individual is somewhat of a stigma as these individuals are looked upon as having no self control and being lazy. Research indicates that obesity may be better managed when treated as a disease condition with behavioral and environmental factors. When the biological factors of obesity and food addiction become more widely understood, obese individual may feel less stigmatized and be more willing to seek assistance through medical intervention.
A multi facet approach including neurobiological intervention and societal acceptance of obesity as a disease (similar to alcoholism) will contribute to managing the prevalence. For example, use of medication to rebuild the supply of dopamine receptors will provide biological/neurological support, allowing individuals to then make better use of behavioral and environmental strategies. Approaching obesity as an addiction to food is a very useful construct in terms of understanding the neural and genetic correlates and possible treatment plans.
In class we talked about obesity as being a problem in “set point”, that like a fever when one is sick, the body’s base setting for weight is too high. In order to fully understand the construct of “set point” and its implications, we must determine what mechanisms are “incorrectly set”. For example, dopamine receptor levels in obese individuals may be “set” too low, causing them to strive for pleasure in food. Similarly, if lepin levels are “set” too low, there may be issues around hunger suppression through the hypothalamus. Paradoxically, obesity may be a problem in a high weight “set point” as the result of certain biological mechanisms being “set” too low. This construct of the “set point” of biological systems being “set” too low is useful in understanding obesity and other forms of addiction.
1) http://www.obesity.org/subs/fastfacts/cities.shtml; American Obesity Association fact sheet
2) Grimm, O. (2007, April/May) Addicted to Food? Scientific American Mind, 18, 36-39. sciammind.com
3) http://www.cnn.com/HEALTH/library/DS/00314.html; CNN Health Library, obesity
4) http://www.sciencemag.org/cgi/reprint/304/5676/1413.pdf; The Obesity Epidemic, sciencemag.org
5) http://www.nature.com/neuro/journal/v8/n5/pdf/nn1452.pdf; How can drug addiction help us understand obesity, Nature Neuroscience
6) http://www.sugarest.com/; Sugarest