"The groundwork of all happiness is health." - Leigh Hunt

Do gut bacteria prevent weight reduction?

Ask the doctor.

Question I just can't drop some pounds. A friend says that my problem could also be because of the variety of bacteria that live in my intestines. This sounds crazy to me, but is it true, and is there anything I can do about it?

Oh Ten years ago, I might have thought your friend was crazy too. Today, I'd say she is likely to be nice. Here's why. We've known for a century that bacteria live in our guts, but we assumed they’d little impact on our health. We thought they were just getting away from us – profiting from the heat and nutrients in our gut.

However, previously decade, remarkable advances have allowed scientists to quantify and characterize the genes in our gut bacteria. The results have been surprising. Our gut bacteria contain 250 to 800 times more genes than human genes. Even more remarkably, these bacterial genes make substances that enter the human bloodstream, affecting our body chemistry. This implies that it’s entirely plausible that the bacteria in our gut can affect our health.

How can they affect our weight? When we eat food, our intestines break it down into smaller pieces. Only small fragments are absorbed into our blood. The rest is disposed of as waste material. In other words, not all of the calories within the food we eat enter our body and make us gain weight. Gut bacteria help break down food. Some bacteria are capable of break down food into small pieces which can be digested, adding calories to our body and thus increasing our weight. Theoretically, if now we have more of such a bacteria in our guts, it must be harder to drop some pounds.

But is there evidence that this is definitely true? Several studies in animals, and a few in humans, suggest that it’s. For example, scientists transferred bacteria from the center of two strains of mice — one which naturally becomes obese and one which is of course lean — to a 3rd strain born lean. I that don’t have gut bacteria. Gut bacteria transferred from naturally obese mice made germ-free mice fat, but gut bacteria transferred from naturally lean mice kept them lean.

The scientists then took bacteria from the center of human similar twins, one fat and one thin, and transplanted the bacteria into the intestines of lean, germ-free mice. The bacteria from the obese twin made the mice fat, however the bacteria from the lean twin didn’t.

We're just starting to grasp the role of gut bacteria in obesity, and science has yet to give you treatments that make weight reduction easier. However, I imagine that day will come.

Photo: © ChrisChrisW/Thinkstock