Obesity Problem Answer Might Be in the Bugs in Our Stomachs

The microbes constitute "a whole ecosystem, and it's evolving on the time scale of minutes," Maley said in releasing the study. Just changing the diet can alter the entire colony of microbes, called the "microbiome," in 24 hours, he said.

The scientists are building on research by others suggesting we have a war going on in our guts.

  • Microbes can affect behavior in vertebrates, as evidenced by research showing one species of microbe "suppresses rats' normal fear of cat smells, often to the detriment of the rats, but to the benefit of the microbes that are ingested into their new feline host," the study says.
  • Many bacteria found in the human gut can manufacture dopamine, the feel-good hormone linked to drug and alcohol addiction, so they can have a dramatic impact on moods. Other microbes can make us crave fats and sugars, contributing to obesity.
  • "Specialist microbes that digest seaweed have been isolated from humans in Japan," the study notes. "African children raised on sorghum have unique microbes that digest cellulose." So some microbes know what they need and may change their host's taste to be sure they get it.

The list goes on and on, sometimes disturbingly.

It's possible that "the obesity epidemic could be contagious as a result of obesity-causing microbes transmitted from person to person," the study says.

That might partly explain why obesity affects entire families, and close friends. The microbes might do that by generating a preference for foods rich in what the microbes are seeking, like fats and sugars.

At this point, the conclusions by the researchers are still in the theoretical stage, but that may change quickly.

"This has been really a blind spot because we tend to think about our bodies as made up just of ourselves," Aktipis said, but a large amount of work in the last five years has been devoted to the possible split-personality of the human microbiome.

We have known for many years that the universe of tiny critters in our guts play an important role in human health, both for good and bad, "but the idea that it would be playing an active role where there would be different interests in different species of microbes competing with us is a new way to think about the nature of our bodies," Aktipis added.

It may not take much to nail this down. The contents of the human gut can be determined through several non-invasive techniques. A mouth swab tells which microbes are at work there.

For researchers who want the "big picture," a stool sample would work, although as Aktipis noted, "some people don't like the idea of giving up their poop."

Physicians treat obese patients all the time, so why not determine the composition of their entire microbiome at the same time? That data from across the country could be fed into a data bank telling which microbes are associated with which public health issues. In time we would have a much better idea of who the enemies are.

After all, this is warfare.

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