Gut bacteria predict weight loss

More than half of all Danes are overweight, and being overweight increases the risk of developing a wide range of diseases, including type 2 diabetes, strokes, various types of cancer, and, currently, an enhanced risk of serious complications resulting from COVID-19 infection.

Globally, more than four million people die from obesity-related illnesses each year. The cost to both individuals and societies is high, and researchers around the world are working intensively to find new ways to help people lose weight.

Obesity has many causes, including genetics and environmental influences such as sedentary lifestyles and diet. Diet is one of the biggest causes of obesity, and most weight loss strategies aim to reduce calorie intake or encourage people to change their diets.

However, people react differently to the same diet. For example, if carbohydrates are omitted from the diet, some people will lose weight and others will gain weight, and so far no studies have been able to clearly explain why.

In a ground-breaking new study recently published in the respected journal Gastroentology, an international team of researchers finds that the composition of bacteria in the gut before starting a weight loss programme is more important than diet and genes. This is an important finding, because it may provide one of the explanations of why people react differently to the same diet, and it opens up for new personal ways to lose weight.

In the study, the researchers examined which of the factors diet, physical activity, obesity-related genotype and the intestinal microbiome (intestinal bacteria and their genes), in the setting of a diet-controlled weight-loss regime would provide the most information about weight loss.

For 24 weeks, 84 subjects followed a low-calorie diet planned by a dietitian, and were in daily dialogue with staff associated with the study. Three days a week, the subjects reported what they ate via a smartphone app that also recorded physical activity and weight, the latter via a scale connected to the internet. 83 of the subjects’ data were good enough to be included in the analysis.

Illustration: Shows the course of the study ranging from the recruitment of subjects over the weight loss period to the analysis and modeling phase and up to the result. Copyright Gastroenterology.

Before the process began, the researchers mapped nine of the genes in the subjects that are linked to an increased tendency to becoming overweight. They then analysed the gut microbiota to find bacteria associated with overweight and slimness, respectively.

These data were then compared to the subjects’ other data and used to determining the best factors for predicting how a weight loss programme will turn out. The result was that the composition of bacteria in the gut before the weight loss process started was by far the best predictor.

This is important knowledge that opens up new possibilities for weight loss. The results pave the way for designing personalized weight loss strategies where the composition of the gut microbiota before starting weight loss is built into the meal plans. Professor Susanne Brix Pedersen from DTU Bioengineering, who took part in the study, explains that it is a field with great potential, but that more basic scientific research is still needed.

“In the long term I expect it will be possible to develop programmes that can be used to give personal dietary advice in connection with weight loss based on one’s microbiota, for example via a smartphone. This would allow you to tailor the diet to increase the number and activity of the bacteria that promote weight loss. We don’t all have the same gut bacteria, so it’s necessary to match the diet to the individual’s composition,” says Susanne Brix Pedersen.

Read the study The baseline gut microbiota directs dieting-induced weight loss trajectories, published in the journal Gastroenterology.