Deadly Sin Gluttony Demystified

       With obesity rates rising in the United States, part of the way people think about obesity is that some individuals just have a taste for food more than others which may lead to a stigma applied to certain parts of the population. It is implied in the article “Simply Irresistible: Scientists Trace Gluttony’s Path in the Brain” that this isn’t exactly the case. Instead, neuroscientists at the University of Michigan have proposed that obese people and addicts have stronger opioid activation of the neostriatum when viewing pictures of food or favorite drug imaged by functional magnetic resonance imaging (fMRI). The neostriatum in humans is located above the well-known reward centers of the ventral striatum and nucleus accumbens. When the neostriatum is activated, an increase level of the neurotransmitter enkephalin emerges. 

To test the theory of whether or not this motor area is responsible for reward activation, tests were conducted with rats by injecting them with a synthetic opioid directly to their neostraitum. In the control group, rats ate about 10 M&Ms in 20 minutes then were satiated and stopped eating. The experimental group that received the opioid injections continued eating after 17 M&Ms and did not show signs of ceasing and had to be forcibly removed from the feeding.  Results of these rats equate to a 150 pound person eating 6 pounds of chocolate within an hour, or the 6 boxes of double stuffed Oreos (in oz). Evidence that also suggest that reward seeking regulation is linked to the neostraitum includes that other chemicals injected in the neostraitum, and artificial opioid and other chemicals injected elsewhere had smaller correlations.

       If opioid activation doesn’t surprise you, a finding about taste preference might. In addition to the injection of a synthetic opioiod, a taste preference test was administered to both control and experimental groups. These results showed that the opioid induced rats had no more preference for chocolate. This suggests that the obesity relates to motor compulsion and reward motivation, not simply overeating for the taste. 

       Evolutionary theories suggest why we have an opioid receptors at all within the brain, and Gary Wenk at Ohio State University mentioned that “the brain helps by activating the opiate system as a euphoric reward, counteracting the discomfort of a swelling waist and encouraging us to have one more bite.” In modern society, we lack the need to overeat at every meal, and if anything, fast food corporations exploit this evolutionary desire to eat plentiful, available, fatty foods. Perhaps looking at obesity from the angle of imbalanced motor control may help increase the understanding of the facets of obesity. 

To read more please visit http://www.scientificamerican.com/article.cfm?id=simply-irresistible-overeating