You Are What You Eat (as Commanded by your Bacterial Masters)

Carl Zimmer has a new posting on his blog that points at new research that may indicate that the plague of obesity might not have anything to do with "weak will" or "self control" but instead point to our puppet master, the microbes that infest us and may be running our feeding for their benefit and to the detriment of our own health:

Can the bacteria in our bodies control our behavior in the same way a puppetmaster pulls the strings of a marionette? I tremble to report that this wonderfully creepy possibility may be true.

The human body is, to some extent, just a luxury cruise liner for microbes. They board the SS Homo sapiens when we’re born and settle into their assigned quarters–the skin, the tongue, the nostrils, the throat, the stomach, the genitals, the gut–and then we carry them wherever we go. Some of microbes deboard when we shed our skin or use the restroom; others board at new ports when we shake someone’s hand or down a spoonful of yogurt. Just as on a luxury cruise liner, our passengers eat well. They feed on the food we eat, or on the compounds we produce. While the biggest luxury lines may be able to carry a few thousand people, we can handle many more passengers. Although the total mass of our microbes is just a few pounds, the tiny size of their cells means that we each carry about 100 trillion microbes–outnumbering our own cells by more than ten to one.

It’s important to bear in mind that you can carry this galaxy of microbes around and enjoy perfect health. These microbes, for reasons that are not entirely clear, behave like well-mannered passengers. They do not barge into the kitchen, take a cleaver to the cooks, and then eat all the food. Aboard the SS Homo sapiens, the crew includes a huge staff of security guards armed with lethal chemical sprays and other deadly weapons, ready to kill any dangerous stowaway (also known as the immune system). For some reason, the immune system does not unleash its deadly fury on the microbes–even when the microbes are fairly close relatives to truly dangerous pathogens.

In fact, our microbial passengers may actually help out the cruise liner’s crew. They can close up the ecological space in our bodies, so that invading pathogens can’t get a solid foothold. Some species in our guts can break down our food in ways that we can’t, and synthesize certain vitamins and other compounds beyond our biochemistry. The genes that the microbes carry–millions of them–expand our biochemical powers enormously.

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I was reminded of this sinister manipulation by a paper that was published in Science today by Rob Knight and his colleagues. They built on previous research that revealed that mice genetically engineered to be obese have different kinds of microbial diversity in their guts than normal mice. Scientists have found that if they transfer microbes from an obese mouse to a regular mouse that has had all its own germs stripped out, the recipient mouse will develop extra fat. In the case of these obese mice, it appears that the microbes become less efficient at helping the animals digest food, triggering a series of changes that leads the mice to be fat.

Read the whole posting. It has a lot more interesting details.

Life and the "real world" is far more complex than we have ever imagined. I get a kick out of the simplistic philosophies and religions that claim a few simple principles dictate everything. The nice thing about science is that it is willing to follow the data no matter how unpleasant or surprising they may be. The fact that we may be controlled by our microbes is a scary thought. But science is willing to investigate.

The good news, we may be able to use our intelligence to break the control of our microbial masters. Rise up ye toiling humans and throw off the chains of your microbial overlords!