A new study may explain why you gain weight after Christmas while your family members stay slim – even if they eat the same food as you.
Researchers have studied how much energy people in Denmark get from their food, based on an analysis of their feces and the microbes in it.
They found that about 40 percent of the participants had microbes that extract more energy from food, on average, than the other 60 percent.
Researchers suspect that similar parts of the population have gut bacteria that are more efficient at extracting energy.
A new study may explain why you gain weight after Christmas while your family members remain thin. Part of the explanation may be related to the composition of our gut microbiota—the trillion-strong community of microbes in the gut.
What is the intestine made of?
Living inside your gut are 300 to 500 different types of bacteria that contain about 2 million genes.
Together with other small organisms such as viruses and fungi, they form what is known as the microbiota.
Like a fingerprint, each person’s microbiota is unique: the mix of bacteria in your body is different from everyone else’s mix.
This is partly determined by your mother’s microbiota – the environment you are exposed to at birth – and partly by your diet and lifestyle.
Bacteria live all over your body, but the bacteria in your gut can have the biggest impact on your well-being.
They line your entire digestive system. Most live in your intestines and colon.
There’s evidence that it affects everything from your metabolism to your mood to your immune system.
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 claim that this is a step toward understanding why some people gain more weight than others, even when they eat the same.
Study author Professor Heinrich Roeser said: ‘We have found a key to understanding why some people gain more weight than others despite not eating as much or differently, but more research is needed.
For the study, experts analyzed gut microbiota from participants’ stool samples – the trillion-strong community of microbes in the gut.
Researchers have described the gut microbiota as ‘like the entire galaxy in our gut’, with 100 billion per gram of faeces.
The research team studied the residual energy in the feces of 85 overweight Danes aged 22 to 66 to estimate 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 participants were divided into three groups, based on the composition of their gut microbes – ‘B-type’, ‘R-type’ and ‘P-type’.
B-type is frequently associated with a Western lifestyle high in microbiota-accessible carbohydrates (MACs) commonly found in fruits and vegetables, compared to P-type, for example, associated with a diet rich in MACs.
The so-called B-type composition (dominated by Bacteroides bacteria), seen in 40 percent of participants, was more effective at extracting nutrients from food, the experts found.
The researchers also found that those who got the most energy from food weighed 10 percent more on average, an extra nine kilograms.
Gut microbiota types
Dominance of Bacteroides bacteria
Dominated by Ruminococcaceae bacteria
Dominated by Prevotella bacteria
In B-type people, the efficiency of extracting nutrients may result in more calories being available from the same amount of food – possibly leading to obesity.
‘Bacterial metabolism of food provides extra energy, for example, short-chain fatty acids – molecules that our bodies can use as fuel to supply energy,’ said Professor Roger.
‘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’s journey through the mouth, digestive tract and anus for each participant, who all had similar dietary patterns.
They hypothesized that those with longer digestive transit times would extract the most energy from their food—but the study found the opposite.
Participants with B-type gut bacteria (the most energy-extracting type) also traveled faster through the gastrointestinal system.
An illustration from a new study. Researchers had hypothesized that those with longer digestive journeys would extract the most energy from their food—but the study found the opposite.
‘Although slower intestinal transit would theoretically allow for more energy excretion, stool energy density was contrary to expectation, positively related to intestinal transit time,’ the team said.
‘This apparent paradox calls for further elucidation of the driving forces shaping the gut microbial ecosystem.’
Although the scientists used only a small sample of Danish participants, it is possible that the findings can be applied to other global populations.
Overall, the results indicate that being overweight may not only 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 guts.
The new study also confirms earlier studies in rodents, including one co-authored by Professor Roger, published in 2016.
In these studies, mice that received gut microbes from obese donors gained more weight than mice that received gut microbes from lean donors, even when fed the same diet.
Gut bacteria in healthy older people become ‘increasingly unique’ as their microbiome produces life-extending chemicals.
Scientists say your gut microbiome — the trillion-strong community of microbes in your gut — can help predict how long and healthy you’ll live.
US researchers have identified distinct signatures in the gut microbiome that are associated with either healthy or unhealthy aging pathways.
In healthy individuals, gut microbiomes are increasingly unique, differing in ways that are unique to the individual compared to unhealthy individuals.
This specificity is linked to microbial-produced amino acid derivatives circulating in the blood, suggesting life-extending chemicals.
This knowledge means microbiomes can be used to predict survival in a population of older people, according to experts.