Some guts are better than others at harvesting

Some guts are better than others at harvesting

photo: Associate Professor Henrik Roager in the laboratory.
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Credit: University of Copenhagen.

New research from the University of Copenhagen suggests that part of the Danish population has a composition of gut microbes that, on average, extract more energy from food than the microbes in the guts of their fellow Danes. The research is a step toward understanding why some people gain more weight than others, even when they eat the same.

As unfair as it is, some of us seem to gain weight just by looking at a plate of Christmas cookies, while others can munch on without a care and not gain an inch. Part of the explanation could be related to the composition of our gut microbes. This was shown by a new study carried out at the Department of Nutrition, Exercise and Sport at the University of Copenhagen.

Researchers studied the residual energy in the feces of 85 Danes to assess how efficient their gut microbes were at extracting energy from food. At the same time, they mapped the composition of gut microbes for each participant.

The results show that approximately 40 percent of the participants belong to the group that on average gets more energy from food compared to the other 60 percent. The researchers also noted that those who got the most energy from food also weighed an average of 10 percent more, which was an extra nine pounds.

“We may have found the key to understanding why some people gain more weight than others, even when they don’t eat more or in any different way. But this needs further research,” says Associate Professor Henrik Roager from the University of Copenhagen’s Department of Nutrition, Exercise and sports.

It may increase the risk of obesity

The results show that being overweight may not be just about how healthy you eat or how much you exercise. It may also have to do with the composition of microbes in a person’s gut.

The participants were divided into three groups, based on the composition of their gut microbes. The composition of the so-called B type (dominates Bacteroids bacteria) is more effective in extracting nutrients from food and was observed in 40 percent of participants.

After the study, researchers suspect that part of the population may be at a disadvantage because they have gut bacteria that are too efficient at extracting energy. This efficiency can result in more calories being available to the human host from the same amount of food.

“The fact that our gut bacteria are excellent at extracting energy from food is basically a good thing, since bacterial metabolism of food provides additional energy in the form of, for example, short-chain fatty acids, molecules that our body can use as fuel to provide energy. But if we consume more than we burn, the extra energy provided by gut bacteria can increase the risk of obesity over time,” says Henrik Roager.

The short intestinal transit time is surprising

From the mouth to the esophagus, stomach, duodenum and small intestine, colon and finally to the rectum, the food we eat travels from 12 to 36 hours, passing through several cells on the way, before the body extracts all the nutrients from the food.

The researchers also looked at the length of this journey for each participant, all of whom had similar eating patterns. Here, the researchers hypothesized that those with long digestive travel times would be the ones to absorb the most nutrients from their food. But the study showed exactly the opposite.

“We thought that a long digestive journey would allow more energy to be extracted. But here we see that the participants with the most energy-extracting B-gut bacteria also have the fastest passage through the gastrointestinal system, which gave us something to think about,” says Henrik Roager.

It confirms previous studies on mice

A new study in humans confirms previous studies in mice. These studies 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, researchers suggested that the differences in weight gain could be attributed to the fact that the gut bacteria of obese people were more efficient at extracting energy from food. This is a theory now confirmed by a new study from the Department of Nutrition, Exercise and Sport.

“It is very interesting that the group of people who have less energy in the stool also have a higher weight on average. However, this study does not provide evidence that these two factors are directly related. We hope to investigate this more in the future,” says Henrik Roager.

About intestinal bacteria:

  • Everyone has a unique composition of gut bacteria – shaped by genetics, environment, lifestyle and diet.
  • The collection of gut bacteria, called the gut microbiota, is like an entire galaxy in our intestines, with an incredible 100 billion of them per gram of stool.
  • Intestinal bacteria in the large intestine are used to break down parts of food that our body’s digestive enzymes cannot, eg dietary fiber.
  • People can be divided into three groups based on the presence and abundance of the three main groups of bacteria that most of us have: B-type (Bacteroids), R-type (Ruminococcaceae) and P-type (Translated).

About the study

  • The energy content of the stool samples of 85 overweight Danish women and men was examined.
  • The participants were men and women aged 22 to 66.
  • 40 percent of the participants belong to a special group, which is characterized by a lower diversity of intestinal bacteria and a faster journey of food through their digestive tract.
  • It was also found that this group had less residual energy in the stool compared to the other two groups, which could not be explained by differences in usual diet.
  • The researchers also noted that the group with less stool energy also weighed more than the other groups.


Henrik Roager

associate professor

Department of Nutrition, Exercise and Sports

University of Copenhagen

[email protected]

+45 35 32 49 28

+45 25 48 06 99

Michael Skov Jensen

Journalist and team coordinator

Faculty of Science and Mathematics

University of Copenhagen

+ 45 93 56 58 97

[email protected]

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