Over-weight? Blame it on gut bacteria

A species of gut bacteria called Clostridium ramosum could enhance the effects of a high-fat diet, leading to weight gain, says a study.

Growth of this organism in the digestive tract is stimulated by high-fat diets, which in turn improves nutrient uptake and enhances the effect of such diets on body weight and body fat, the findings suggested.

"Our results indicate that Clostridium ramosum improves nutrient uptake in the small intestine and thereby promotes obesity," said co-researcher Michael Blaut from the German Institute of Human Nutrition.

The researchers observed that mice harbouring human gut bacteria including C. ramosum gained weight when fed a high-fat diet.

Mice that did not have C. ramosum were less obese even when consuming a high-fat diet, and mice that had C. ramosum but consumed a low-fat diet also stayed lean.

"Previous studies have found C. ramosum and other representatives of the Erysipelotrichi class in obese humans," Blaut stressed.

For the study, the researchers investigated the role of C. ramosum in three groups of mice: some harboured a simplified human intestinal microbiota (bacteria) of eight bacterial species including C. ramosum; some had simplified human intestinal microbiota except for C. ramosum and some had C. ramosum only.

"We were surprised that presence or absence of one species in a defined bacterial community affected body weight and body fat development in mice," Blaut pointed out.

The study appeared in the journal mBio.