Your Brain on Food

How chemicals control your thoughts and feelings.

How a worm might one day cure obesity

This idea might sound disgusting at first, however...

In order to understand how a worm might some day prevent you from developing Alzheimer's disease or even slow the aging process you need to stand naked in front of a mirror.  Look closely - really closely! Put on a pair of magic glasses that allows you to see the immense multitude of creatures looking back at you.  For every 1 of your big human cells, roughly 100 to 1000 little bugs live alongside and inside of you. If you were to count all of the cells on and inside of you that are not actually YOU, they would number in the tens of trillions, with approximately 1 million of these microbes living within every square centimeter of your skin!  You are never really alone. These little bugs that have hitched their fortunes to you contribute to your good health as well as to your sickness. As our species and theirs evolved, we established some rules to govern our cohabitation, and most of the time everything works out fine; however, like an unpredictable roommate, these bugs can turn against us, and their impact on brain function can be profound because they share our body's exposure to the drugs and foods we consume.

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Obesity induces an imbalance in body's intricately choreographed dance with these little creatures.  Obese patients with Alzheimer's disease actually have more pathology in their brains and a more rapid mental decline.  Obesity first ages us, then impairs our memory and then finally kills us. Being obese at mid-life is also a strong predictor of dementia in later life. Why? It's because during the process of depositing and filling fat cells, another cell type, called a macrophage, becomes embedded amongst our fat cells.  Macrophages are part of our body's immune defense system and when they are surrounded by fat cells these macrophages start releasing chemicals that impair the body's ability to regulate glucose and fat metabolism while also making our bodies insensitive to insulin: this is known as the dreaded Metabolic Syndrome.

How can we turn off these nasty macrophages?  The hero of our story is a cell called eosinophil.  The more of these eosinophils you have in your body the better able you are to reverse the negative effects of macrophages.  One of the most effective signals for inducing your body to produce more eosinophils is infection by parasitic worms.  A group of scientists at the University of California at San Francisco decided to test this idea.  When obese mice were given a fatty diet and then infected with such a parasitic worm their body fat disappeared and glucose tolerance was restored!

I realize that this idea sounds disgusting but just keep in mind that your new parasitic companion would have lots and lots of company, you would lose lots of weight and after a little while you would become accustomed to those subtle undulations within your abdomen as the worm grew ever larger while consuming all of your body fat.  There's good news however: The scientists discovered that the worm need only spend a week within your gut in order for you to benefit from its ability to activate your eosinophils.

This study has some broad implications related to the impact of our overly hygienic lifestyle in developed countries that often have the greatest percentage of obese citizens.  We co-evolved with many different parasitic species; we still carry many of them around with us all of the time.  Thus, inviting into our bodies just one more parasitic worm could become an integral part of a new Paleolithic diet plan.  

© Gary L. Wenk, Ph.D., author of Your Brain on Food (Oxford, 2010)

Gary L. Wenk, Ph.D., is a Professor of Psychology & Neuroscience & Molecular Virology, Immunology and Medical Genetics at the Ohio State University.

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