Gut Bacteria May Cause More Weight Gain with a High-Fat Diet

Could gut bacteria be contributing to obesity? Scientists have found that a species of gut bacteria called Clostridium ramosum, coupled with a high-fat diet, may cause animals to gain weight.

Gut bacteria can regulate our digestive systems. In fact, past studies have found that the makeup of bacteria in our guts can largely impact our health. That's why scientists decided to take a closer look at which gut bacteria cause what impacts.

Previous studies found that C. ramosum and other representatives of the Erysipelotrichi class are located in obese humans. This suggests that the growth of this organism in the digestive tract is stimulated by high-fat diets. This, in turn, improves nutrient uptake and can enhance the effects of these diets on body weight and body fat.

In order to better understand the impacts of these bacteria, the scientists examined the role of C. ramosum in the guts of mice. One group of mice had simplified human gut bacteria, including C. ramosum; another group had simplified human gut bacteria without C. ramosum; and a third group only had the specific gut bacteria. Then, the mice were fed a high-fat diet for about four weeks.

So what did the scientists find? The first group and the third group gained significantly more body weight and body fat than the group without C. ramosum. This implies that the mice converted food more efficiently to energy. In contrast, all of the mice fed a low-fat diet stayed lean, which indicates that the obesity effect of C. ramosum only occurs with a high-fat diet.

"Our results indicate that Clostridium ramosum improves nutrient uptake in the small intestine and thereby promotes obesity," said Michael Blaut, one of the researchers, in a news release. "This possibly means that there is more than one mechanism underlying the promotion of obesity by intestinal bacteria."

The findings are published in the journal mBio.