Specific Gut Bacteria Extract More Energy Which Seems to be Associated with Obesity
Certain hyper-efficient microbe species in our guts could be the reason why some people gain weight and others don’t, proving once again how much influence the microbiota has in our lives.
Unfair as it is, some of us seem to put on weight just by looking at a pizza while others can munch away with abandon and not gain a gram. Part of the explanation could be related to the composition of our gut microbes.
Researchers 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 extracts more energy on average 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 9 kilograms, or around 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 of the University of Copenhagen’s Department of Nutrition, Exercise and Sports, which ran the study.
The results indicate that being overweight might not only be related to how healthily one eats, the amount of exercise one gets, or their sleep quality. It may also have something to do with the composition of a person’s gut microbes.
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 a portion of the population may be disadvantaged by having gut bacteria that are a bit too effective at extracting energy.
This effectiveness may result in more calories being available for the human host from the same amount of food—an adaptation which would have been of great value to early man, but during the age of abundance could be leading to obesity.
“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,” explains Henrik Roager.
The study also looked at the total length of GI tract, from mouth to stomach to the intestines and colon, to see whether variations in a food’s journey time between individuals affected weight gain.
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.
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“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 Dr. Roager.
These findings in humans confirm earlier studies in mice, which showed that germ-free mice which 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.
“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,” Dr. Roager.
If it were to be confirmed scientifically that the two are correlated, the widely-publicized fecal matter transplant, which essentially shares a donor’s flourishing microbiota with a patient’s disrupted one, could be used to combat this natural tendency towards weight gain.
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