A new study may explain why you put on weight after Christmas while your family members stay thin — even when they eat the same amount as you.
Researchers have studied how much energy Danes derive from their food, based on analysis of their faeces and the microbes present.
They found that about 40% of participants have microbes that, on average, extract more energy from food compared to the other 60%.
The researchers suspect that similar portions of populations might be harmed by having gut bacteria that are very effective at extracting energy.
A new study may explain why you pack on weight after Christmas while your family members stay thin. Part of the explanation may relate to the makeup of our gut microbiota – the community of trillions of microorganisms in the gut.
The new study, published in the journal Microbiome, was conducted by experts from the Department of Nutrition, Exercise and Sport at the University of Copenhagen.
The authors say it’s a step towards understanding why some people gain more weight than others, even when they eat the same.
“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, experts analyzed the gut microbiota – the community of trillions of microorganisms in the gut – from the participants’ stool samples.
Researchers describe the gut microbiota as “an entire galaxy in our gut,” with a staggering 100 billion of them per gram of stool.
The research team studied the residual energy in the stool of 85 overweight Danes, aged between 22 and 66 years, to estimate the effectiveness of their gut microbes in extracting energy from food.
At the same time, they mapped the composition of each participant’s gut microbes.
Participants were divided into three groups based on the composition of their gut microbes – ‘B-type’, R-type’ and ‘P-type’.
Type B has been repeatedly associated with a Western lifestyle low in microbiota-accessible carbohydrates (MACs), typically found in fruits and vegetables, compared with type P, for example, associated with a diet high in MACs.
The so-called B-type composition (dominated by Bacteroides bacteria), seen in 40% of participants, was more effective at extracting nutrients from food, the experts found.
The researchers also found that those who extracted the most energy from food weighed 10% more on average, totaling nine pounds more.
The efficiency of nutrient extraction in type B people can result in more calories being available from the same amount of food – possibly leading to obesity.
“Bacteria’s metabolism of food provides extra energy in the form of, for example, short-chain fatty acids – molecules that our bodies can use as energy-supply fuel,” said Professor Roager.
‘But if we consume more than we burn, the extra energy provided by gut bacteria can increase the risk of obesity over time.’
The researchers also studied the duration of food travel from the mouth, digestive system and rectum for each participant, who all had similar eating patterns.
They hypothesized that those with the longest digestive travel times would extract the most energy from their food – but the study found the opposite.
Participants with type B gut bacteria (the type associated with extracting more energy) also had the fastest passage through the gastrointestinal system.
“Although slower intestinal transit theoretically allowed for more energy extraction, stool energy density was, contrary to expectations, positively associated with intestinal transit time,” say the team.
New study illustration. The researchers had hypothesized that those with the longest digestive travel times would be the ones who extracted the most energy from their food – but the study found the opposite.
“This apparent contradiction requires further deciphering the driving forces that shape the gut microbial ecosystem.”
Although the scientists only used a small sample of Danish participants, it’s possible that the findings could be applied to other global populations.
Overall, the results indicate that being overweight may not just be related to how healthy a person eats or the amount of exercise they do, but it 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, 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 being fed the same diet.
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