Getting slim with the right gut bacteria

In the fight against obesity, another factor beyond a negative energy balance -- that is, consuming fewer calories than we burn -- is becoming increasingly important: The composition of gut bacteria. In technical jargon this is called "microbiome." The microbiome can be imagined as an independent ecosystem that only functions optimally when certain bacteria have a large number of germs.

"Fat" or "thin" depends on composition of gut bacteria

Whether we are fat or thin depends largely on which intestinal bacteria colonize our intestines. Studies have shown that overweight people have a different microbiome than thin people. This means that the composition of the different bacteria in their bodies differs significantly from the bacterial community that is found in those without a weight problem.

While the Bacteroides strains and the Bifidobacteria belong to the "slimming bacteria," for instance, the Firmicutes strains belong to the "fattening bacteria." Really, all these bacteria exist in the intestine. But when the ratio of slimming bacteria to fattening ones is disturbed and shifted towards Firmicutes, it becomes hard to lose weight.

Effects of gut bacteria imbalance

If the bacterial distribution changes only slightly -- for example, if more Firmicutes settle in the intestine -- they gain up to 10 percent more calories from the food, because they are able to extract energy even from dietary fiber, which the human digestive tract normally can not process. In our ancestors, these fattening bacteria were vital to survival in times of hunger because they could also extract calories from grass or tree bark. In today's affluent society, they are fatal. By breaking down dietary fibers from vegetables, whole grains and fruit, the fattening bacteria can absosrb between 150 and 250 calories per day. By the end of the year, this represents 10 kg (22 pounds) of extra weight. This mechanism throws all calorie tables off, because it means the body can draw calories even from a salad leaf when gut bacteria is out of balance.

To top it off, the Firmicutes bacteria, together with the cells of the intestinal wall, also produce certain hormones that control our feeling of hunger. This means that the natural feeling of fullness is disrupted and we automatically eat more. Even worse: These bad bacteria influence our taste and direct our appetite towards eating sweets.

Composition of healthy gut bacteria

Gut bacteria is healthy if the Bacteroides and Bifidobacteria set the tone. These bacteria should count at least twice as much as the Firmicutes. Slender people often have up to 90 percent of the slimming bacteria and only 10 percent Firmicutes, while good "feed converters" have exactly the opposite composition. The role of lactic acid bacteria, known as Lactobacillus, which we find in yogurt and other dairy products, is still unclear. Effects depend on the individual subgroups, which according to studies, show both weight gain and weight loss. While it is not necessary to stay away from dairy products, it is recommended to avoid excessive intake of lactic acid products.

The composition of intestinal flora, such as the relationship between Bacteroides and Firmicutes, can be assessed through a stool sample.