The microbes in your gut influence your ability to lose weight, a study from the Institute for Systems Biology in Seattle, USA, has found.


Previous research has shown that changing your diet can alter the composition of your gut microbiome. The team suggest that, if you’re struggling to lose weight, you may be able to encourage more beneficial microbes in your gut by changing what you eat.

“Your gut microbiome can help or cause resistance to weight loss and this opens up the possibility to try to alter the gut microbiome to impact weight loss,” said lead author Dr Christian Diener.

Participants in the study were not given a specific diet or exercise regime, but instead were assigned a dietician and a nurse coach to lead them through a commercial wellness programme.

Out of the 5,000 people who took part in the programme, the researchers focussed on 105, who were split into two groups: 48 had lost over 1 per cent of their body weight over the course of 6-12 months, and the other 57 had a stable BMI over the same time.

The researchers gathered blood and stool samples from the participants, and studied the genetic material recovered from them. They also looked at proteins found in the blood, analysed dietary questionnaires, and deduced what gut bacteria could be found in each group.

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After controlling for age, sex and BMI, the team found that some gut bacteria conferred a resistance to weight loss, whereas others helped weight loss. In those who didn't lose weight, the gut microbiome were better at breaking down starches. In other words, the bugs in their gut were better at getting to the complex calories in food.

However, in those who did, the researchers found more evidence of microbial DNA that allow bacteria to grow, replicate and assemble cell walls more quickly. This means the bacteria ate more of the sugar before the body could absorb it.

“Before this study, we knew the composition of bacteria in the gut were different in obese people than in people who were non-obese, but now we have seen that there are a different set of genes that are encoded in the bacteria in our gut that also responds to weight loss interventions,” said Diener.

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“The gut microbiome is a major player in modulating whether a weight loss intervention will have success or not. The factors that dictate obesity versus non-obesity are not the same factors that dictate whether you will lose weight on a lifestyle intervention.”

Reader Q&A: Do we get our gut bacteria microbiome before or after birth?

Asked by: Michael Chandler, Hereford

We each have trillions of bacteria living in our gut and this microbiome plays important roles in digestion and fighting disease. Their origins have long been debated, but two large-scale studies in 2019 offered some answers.

In one, researchers retrieved more than 500 placentas from women shortly after giving birth, and found the healthy placentas were sterile. Another study reported that babies delivered by caesarean lack certain strains of beneficial bacteria. Taken together, the research indicates we pick up our microbiome during and shortly after birth.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.