My answer is YES, all the time, no exceptions!  Do you remember when Miranda from “Sex and the City” was so addicted to chocolate cake that even after she threw it away, she pulled a piece of cake out of the trashcan and ate it?  No doubt we have all had a moment when we knew we should stop but it was impossible to resist even when we are not hungry!  So, why do we indulge in sweets?  Is it because of our emotions, or is it due to chemicals in our brains?

Recently, researchers found new evidence to explain our uncontrollable urge to overeat such deliciously sweet and fatty treats.  In the study by DiFeliceantonio et al., which was published in the September issue of Current Biology, a natural opioid peptide called enkephalin was measured in the rat neostriatum, an area of the brain that naturally produces enkephalin and is involved in motor movement.  Researchers implanted a small probe in the rat’s brain and gave it unlimited access to chocolate M&Ms.  Remarkably, the level of enkephalin was greatly elevated when the rats were consuming M&Ms!

To see if the spike of enkephalin was causing the binge eating or if the binge eating itself induced the surge of enkephalin, researchers injected enkephalin directly into the neostriatum.  Surprisingly, addition of this chemical to the neostriatum triggered the desire to eat junk foods, as these rats gorged themselves with more than twice the amount of chocolate M&Ms than they would have otherwise eaten!

But why did the rats eat more M&Ms?  Did the M&Ms taste better, or did enkephalin cause them to overeat?  To answer this question, they analyzed the rats’ facial expressions (lip licking) while they were given M&Ms and other tastes.  They found that the number of lip licks remained the same, indicating that enkephalin did not make the M&Ms taste better.  Rather, enkephalin stimulated the rats to eat more and quickly.  In other words, the elevation of enkephalin increased their motivation to overeat M&Ms!

According to the authors, the neostriatum is active not only when obese people see foods, but also when drug addicts see drug scenes.  This study suggests that the neostriatum is involved in the “over-consume” reward systems of the brain, an unexpected and exciting finding!

This research showed us that a chemical compound in our brain, enkephalin, increases the motivation to eat, which eventually changed the eating behavior.  All this is happening in the neostriatum, which has now been shown to be involved in reward-function in the brain.  So, when the craving pops up, now we can describe it as, “Oooh, there’s a surge of enkephalin going on in my brain and pumping up my motivation to eat more!”

~

References:

DiFeliceantonio, A., Mabrouk, O., Kennedy, R. & Berridge, K. (2012). Enkephalin Surges in Dorsal Neostriatum as a Signal to Eat, Current Biology, 22 (20) 1924. DOI:10.1016/j.cub.2012.08.014
Image adapted from Flickr/Alfonsina Blyde
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Jooyeun Lee

Jooyeun (JL) dreamt about being an artist and yet she is now in her fifth year as a Neuroscience Ph.D. student at USC.As she studied art in college, it opened up a whole new world beyond her perspective and turned out earning a Bachelor’s degree in Biology.Thereafter, she joined a neuroscience lab at California State University, Northridge, studying wound healing response in diabetic neuropathy as her Master’s thesis project.Currently, she studies neurological disorders, such as Down syndrome and Alzheimer’s disease, using Drosophila as a model system.
Profile photo of Jooyeun Lee

Jooyeun Lee

View posts by Jooyeun Lee
Jooyeun (JL) dreamt about being an artist and yet she is now in her fifth year as a Neuroscience Ph.D. student at USC. As she studied art in college, it opened up a whole new world beyond her perspective and turned out earning a Bachelor’s degree in Biology. Thereafter, she joined a neuroscience lab at California State University, Northridge, studying wound healing response in diabetic neuropathy as her Master’s thesis project. Currently, she studies neurological disorders, such as Down syndrome and Alzheimer’s disease, using Drosophila as a model system.

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