Microbes may be to blame for gaining weight at Christmas, study suggests

A new study could explain why you gain weight after Christmas while your family members stay lean, even when they eat the same amount as you.

Researchers have studied how much energy Danes take in from their food, based on analysis of their feces and the microbes they contain.

They found that about 40 percent of the participants have microbes that, on average, extract more energy from food compared to the other 60 percent.

The researchers suspect that similar portions of populations may be disadvantaged by having gut bacteria that are too effective at extracting energy.

The new study, published in the journal Microbiome, was led by experts from the Department of Nutrition, Exercise and Sports at the University of Copenhagen.

The authors say it’s a step toward understanding why some people gain more weight than others, even when eating the same things.

“We may have found a key to understanding why some people gain more weight than others, even when they don’t eat more or differently, but this needs to be investigated further,” said study author Professor Henrik Roager. .

For the study, the experts analyzed the intestinal microbiota, the community of millions of microorganisms in the intestine, from stool samples of the participants.

The researchers describe the gut microbiota as “like a whole galaxy in our gut,” with a staggering 100 billion per gram of faeces.

The research team studied residual energy in the feces of 85 overweight Danes aged 22 to 66 to estimate how effective their gut microbes were in extracting energy from food.

At the same time, they mapped the composition of each participant’s gut microbes.

The participants were divided into three groups, based on the composition of their gut microbes: ‘type B’, type R’ and ‘type P’.

Type B has been repeatedly linked to a western lifestyle low in microbiota-accessible carbohydrates (MAC) typically found in fruits and vegetables, compared to type P, for example, linked to a diet rich in MAC.

The so-called type B composition (dominated by Bacteroides bacteria), seen in 40 percent of the participants, was most effective at extracting nutrients from food, the experts found.

The researchers also found that those who extracted the most energy from food weighed 10 percent more on average, which was an extra nine kilograms.

The efficiency of extracting nutrients in type B people may result in more calories being available from the same amount of food, possibly leading to obesity.

‘The metabolism of food by bacteria provides additional energy in the form of, for example, short-chain fatty acids, molecules that our bodies can use as fuel for energy supply,’ said Professor Roager.

“But if we consume more than we burn, the additional energy provided by gut bacteria may increase the risk of obesity over time.”

The researchers also studied the journey time of food from the mouth, digestive system, and rectum for each participant, all of whom had similar dietary patterns.

They hypothesized that those with the longest digestive journey times would extract the most energy from their food, but the study found otherwise.

Participants with type B gut bacteria (the type associated with extracting the most energy) also had the fastest passage through the gastrointestinal system.

“Although slower intestinal transit would theoretically allow for greater energy extraction, fecal energy density was positively associated, contrary to what might be expected, with intestinal transit time,” the team says.

“This apparent contradiction requires further unraveling of the driving forces that shape the gut microbial ecosystem.”

Although the scientists only used a small sample of Danish participants, it is possible that the findings could be applied to other global populations.

Overall, the results indicate that being overweight might not only be related to how one eats healthily or how much exercise one gets, but may also have something to do with the microbes in our gut.

The new study also confirms previous studies in rodents, including one co-authored by Professor Roager that was published in 2016.

In these studies, rodents that received gut microbes from obese donors gained more weight compared to rodents that received gut microbes from lean donors, despite receiving the same diet.