Are the Bugs in Your Gut Making You Gain Weight?

At this very minute there are more than a hundred trillion tiny bacteria and other microbes living in your intestines. Although they are microscopic, all together they weigh about three pounds which is more than the weight of the average human brain. Researchers are just starting to investigate the role these microbes play in digestion, weight gain and other aspects of health. It’s possible that some gut microbes are better able to extract calories from food making weight gain more likely. While the exact effect of a specific microbe isn’t known, it’s thought that, in addition to obesity, microbes can affect everything from allergies and inflammation, to diabetes and even depression and anxiety.

In a now-classic study, researchers at Washington University in St. Louis found pairs of twins where one was obese and the other wasn’t. They transplanted fecal matter (poop) from the twins into mice. They found that, after five weeks, mice receiving bacteria from the fatter human twin had 15 to 17 percent more body fat than the mice who got the bacteria from the thin twin. The findings suggest that the bacteria residing in our guts can play a role in determining weight although the specific types of bacteria involved haven’t been identified. As a result it will probably be years before an effective bacteria based, probiotic treatment for obesity is developed.

While there’s no currently available microbial treatment and many of the microbes in your body are inherited or established early in life by being breast or bottle-fed, the types of food you eat may alter the variety of microbes residing in your intestines. The typical American diet that is rich in sugar and processed foods may contribute to more unhealthy microbes and bacteria but a recent study found that people who had a mostly plant-based diet had a richer, more diverse microbe population. A plant-based diet also increased good bacteria that promote health. Although it’s not known how long it takes for dietary changes to alter the intestinal microbes and bacteria, it’s likely that a diet high in fiber from fruit, vegetables, whole grains and nuts or seeds may increase the good little bugs. So now you have another reason to increase the fruit, vegetables and unprocessed foods in your diet.