Firmicute bacteria in a laboratory culture. New findings suggest that the composition of your intestinal microbe community could help determine how easily you gain weight.

Credit: Wikipedia

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PARIS: Certain gut bacteria may encourage obesity, according to research reported this week in the British journal Nature.

"This is a potentially revolutionary idea that could change our views of what causes obesity and how we depend on the bacteria that inhabit our gut," wrote independent researchers from the University of Cincinnati in a commentary on the work.

Living in the intestine of all humans are trillions of bacteria that assist our own stomach acids and enzymes in breaking down food. Two groups - the Firmicutes and the Bacteroidetes - together account for more than 90 per cent of intestinal bacteria.

U.S. researchers compared the gut bacteria of obese and lean people, and found that obese people had fewer Bacteroidetes than their slender counterparts.

To work out whether the trend was linked to diet, the team, led by Jeffrey Gordon of Washington University in St Louis, studied 12 obese people who went on a diet for a year. The subjects ate food that was low in either fat or carbohydrates, and the team monitored their gut bacteria composition.

Before the diet, the intestines of the obese group were higher in Firmicutes and lower in Bacteriodetes than a comparison group of lean individuals. But as the diet progressed, the Firmicutes reduced and the Bacteriodetes increased in number.

The researchers took this discovery further in experiments with mice, finding that the gut bacteria of obese mice not only had fewer Bacteroidetes than their skinny counterparts, but also that their bacterial genome was rich in genes that broke down hard-to-digest foods more efficiently.

Fewer calories remained in the faeces of the obese mice compared with the lean ones, which, according to the scientists, implies that the chubby rodents were able to extract more energy from their food thanks to their intestinal flora.

To make certain that the difference in gut bacteria was the reason behind the obese rodents' digestive prowess, the team actually transferred the gut microbes from obese mice to skinny mice. Notably, the skinny mice that received the transfer gained weight.

The rise in obesity in developed countries is ascribed almost universally to a shift to high-fat, high-sugar diets and a sedentary lifestyle over the past few decades. But scientists are also interested in additional factors that could explain why the obesity crisis has emerged so quickly and why some individuals are more prone to fat gain than others.