Nov 27, 2010 Mary Desaulniers
Fat Addiction in Rats - Jepoirrier Image
Even a cursory glance at television commercials reveals the problem of fat addiction in our culture. Ads for fast food, chips, crackers and meals on the run have become the staples of family entertainment. It is no wonder that food addiction and obesity are fast becoming major problems in North America. Even more worrisome is the idea that excess food intake threatens not only the waistline, it is also a liability to the brain.
According to recent research led by Paul Kenny Ph.D at the Scripps Research Institute in Jupiter, Florida, overeating can change the brain, triggering alterations that create a neurochemical addiction in the eater. Although this dependency has been shown in rats, its observations can be carried over into the human arena where similar brain changes have been seen in people addicted to drugs.
Overeating, like Drug Addiction, Creates Brain Irregularity
Because eating is such a pleasurable activity, it can produce behavior patterns similar to other pleasurable activities like sex or drug use. Eating initiates the release of dopamine, a feel-good neurotransmitter in the brain. Repeated episodes of overeating increase the likelihood that the activity becomes habitual.
Because of the neuroplasticity of the brain,repeated behavior rewires or changes the brain. Neurochemical patterns produced by excessive drug use, for example, can become hardwired into a compulsion. The molecular pathways behind drug addiction are similar to those created by food or fat addiction.
Rats Fed High Fat Foods Become Hooked on Fat
In the study led by Kenny and his group, rats were divided into three groups. Group A had almost unlimited access to high fat treats like sausages, bacon, chocolate and cheesecakes. Group B had limited access - one hour a day to these junk foods while Group C, the control group, was given no access at all to human food. All three groups had free access to water and healthy "lab rat chow."
Group A showed little interest in the lab rat fare; they gorged themselves and became obese. Similarly, Group B rats consumed almost two-thirds of their daily calories with one hour feeding per day, "developing a pattern of compulsive binge eating."
Examining the rats, researchers found that fat overstimulation has produced a brain adaptive response in Groups A and B. Their dopamine release centers, known as D2 receptors, have decreased, forcing them to eat more to get the same effects from the pleasure chemicals.
In the same way a drug user requires more frequent doses of the drug for satiation, these fat addicted rats require more junk food to reach their satiation point.
Fat Addiction in Humans Linked to Fewer D2 Receptors
Studies have shown that the number of dopamine receptors known as D2 receptors are low in the brains of many obese people. A particular genetic abnormality has already been linked to fewer D2 receptors, drug addiction and obesity.
Kenny's study has led researchers to speculate that food addiction can be caused either a genetic brain irregularity or a maladaptive behavior altering the neurochemical profile of the brain.
We know that overeating can be initiated by stress. Studies have linked high levels of cortisol with increased cravings for fat, sugar and weight gain, especially in premenopausal women who, after being subjected to laboratory induced stress, chose to consume more foods high in sugar and fat. Cortisol also triggers the release of hormones and neuropeptides that stimulate appetite.
This choice of food as a response to stress can become habituated into a hard to break compulsion. Such was the case with the obese rats whose fat addiction was so fierce they continued to gorge themselves on junk food even when they were threatened by electric shocks. Moreover, when their fat-laden fare was stopped, the rats refused to eat the standard rat chow provided for them for an average of 14 days. They would rather starve than return to healthy fare - an indication of the intensity of their food addiction.
Milkshakes and cheeseburgers were certainly not on the menu of our forefathers. Now staples in our North American culture, they could be exerting a less than desired influence on our brain and behavior. According to researcher Kenny, "this energy-dense stuff is very new to us as a species. It's probably corrupting our brain circuitry." Much food for thought here - especially for caution during food addiction seasons like Thanksgiving and Christmas!
Sources:
- Harding, Matthew,"Junk Food's Addictiveness Re-evaluated," DigitalJournal.com, March 29, 2010, accessed November 25, 2010.
- Harmon, Katherine,. "Addicted to Fat: Overeating May Alter the Brain as Much as Hard Drugs," Scientific American Online. March 28 2010, accessed November 25, 2010.
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