New findings are a step towards understanding why some people gain more weight than others, even when they eat the same diet.
The research indicates that some Danish people have a composition of gut microbes that, on average, extracts more energy from food than do the microbes in the guts of their fellow Danes. Part of the explanation could be related to the composition of their gut microbes.
Researchers at the University of Copenhagen’s department of nutrition, exercise, and sports studied the residual energy in the feces of 85 Danes to estimate how effective their gut microbes are at extracting energy from food. At the same time, they mapped the composition of gut microbes for each participant.
The results show that roughly 40% of the participants belong to a group that, on average, extracts more energy from food compared to the other 60%. The researchers also observed that those who extracted the most energy from food also weighed 10% more on average, amounting to an extra nine kilograms (about 20 pounds).
“We may have found a key to understanding why some people gain more weight than others, even when they don’t eat more or any differently. But this needs to be investigated further,” says associate professor Henrik Roager.
The results indicate that being overweight might not be related to how healthily a person eats or the amount of exercise they get. It may also have something to do with the composition of their gut microbes.
As reported in the journal Microbiome, participants were divided into three groups, based on the composition of their gut microbes. The so-called B-type composition (dominated by Bacteroides bacteria) is more effective at extracting nutrients from food and was observed in 40% of the participants.
Following the study, the researchers suspect that having gut bacteria that are more effective at extracting energy may result in more calories being available for the human host from the same amount of food.
“The fact that our gut bacteria are great at extracting energy from food is basically a good thing, as the bacteria’s metabolism of food provides extra energy in the form of, for example, short-chain fatty acids, which are molecules that our body can use as energy-supplying fuel. But if we consume more than we burn, the extra energy provided by the intestinal bacteria may increase the risk of obesity over time,” says Roager.
From mouth to esophagus, stomach, duodenum, and small intestine, large intestine, and finally to rectum, the food we eat takes a 12-to-36-hour journey, passing several stations along the way, before the body has extracted all the food’s nutrients.
The researchers also studied the length of this journey for each participant, all of whom had similar dietary patterns. Here, the researchers hypothesized that those with long digestive travel times would be the ones who harvested the most nutrition from their food. But the study found the exact opposite.
“We thought that there would be a long digestive travel time would allow more energy to be extracted. But here, we see that participants with the B-type gut bacteria that extract the most energy, also have the fastest passage through the gastrointestinal system, which has given us something to think about,” says Roager.
The new study in humans confirms earlier studies in mice. In these studies, researchers found that germ-free mice that received gut microbes from obese donors gained more weight compared to mice that received gut microbes from lean donors, despite being fed the same diet.
Even then, the researchers proposed that the differences in weight gain could be attributable to the fact that the gut bacteria from obese people were more efficient at extracting energy from food. The new research confirms this theory.
“It is very interesting that the group of people who have less energy left in their stool also weigh more on average. However, this study doesn’t provide proof that the two factors are directly related. We hope to explore this more in the future,” says Roager.
Source: University of Copenhagen
