Do gut microbes play a role in weight loss?

Paper of the Month for May

The Paper of the Month for May is from Proceedings of The Nutrition Society and is entitled ‘Personal diet–microbiota interactions and weight loss' by Henrik M. Roager and Lars H. Christensen.

Together with a friend, you decide to lose weight by changing your diet. Unfortunately, only your friend is successful in reaching their goal weight. While there can be many reasons for your lack of success, one reason might be hidden in your gut.

Each of us carries around a unique combination of gut microbes, known collectively as the gut microbiome. Your gut microbiome has been shaped by your diet and environment throughout your life, and it is modified constantly by your lifestyle choices. Your resident gut microbes are not passive passengers – they insist on helping you digest your food and they communicate with your own cells through the production of small signalling molecules.

It is over 15 years since scientists elegantly demonstrated the effect of the gut microbiome on body weight. They colonised germ-free (sterile) mice with microbes from either an obese donor or microbes from a lean donor. Despite being fed the same diet and consuming the same calories, the body weight of the mice differed according to which microbes they had been given. It was proposed the two compositions of microbes differed in their ability to extract energy from food. These intriguing findings sparked a huge interest in research into the microbiome. However, while the findings were subsequently replicated in other animal studies, clear evidence of relationships between specific microbiome-compositions and energy extraction capacity was not found in human studies.

Nonetheless, in recent years several human dietary intervention studies have found that specific microbiome signatures or specific gut microbes could be predictive of weight loss success. This has fuelled new interest in the field and several hypotheses have been put forward.

Research is therefore now trying to figure out how your gut microbes respond to the food you eat. We need to know more about this because the personal fermentation responses in the colon may be the key to improving our understanding of differences between individuals in weight loss in response to a change in diet.

In brief, we hypothesise that your weight loss success could depend on the ability of your gut microbes to extract energy from your diet, as well as their ability to produce small signalling molecules, which could affect your energy metabolism and appetite.

We are not there yet, but the hope is that if we understand the factors that determine colonic fermentation responses to foods, we could potentially tailor a diet to your personal gut microbiome and thereby increase the likelihood of you achieving a successful weight loss – just like your friend.