The reason one diet does not suit all may be found in our guts. Our previous research showed that microbes in the digestive track, known as the gut microbiota, are linked to the accumulation of belly fat. Our gut microbiota is mostly determined by what we eat, our lifestyle and our health. So it is difficult to know exactly how food and gut microbes together influence fat accumulation and ultimately disease risk. Our latest study provides new insights into these interactions.
Animal studies have been valuable in showing that gut microbes alone can reduce the build-up of fat, resulting in better health. But translating these findings to humans is difficult, especially considering that we can eat very different foods.
Gut microbes don’t lie
In our study, we aimed to disentangle the effect of gut microbes and diet on the accumulation of belly fat in 1,700 twins from the UK. We found that the composition of the gut microbiota predicts belly fat more accurately than diet alone.
We identified a few specific nutrients and microbes that were bad for us and linked to an increase in belly fat, as well as a few nutrients and many microbes that were good for us and linked to reduced belly fat. The observed link between belly fat and bad nutrients, such as cholesterol, was not affected by the gut microbiota.
In contrast, we found that the gut microbiota plays an important role in the beneficial effect of good nutrients, such as fibre or vitamin E. We show that specific gut bacteria play an important role in linking certain beneficial nutrients to less belly fat. In other words, changes in a person’s diet are less likely to lead to weight loss if the relevant bacteria are not in their gut.
Diet alone did not have a strong impact on the observed links between gut microbes and belly fat, as specific gut bacteria were linked to belly fat accumulation regardless of diet. This confirms what was previously seen in mice, that gut microbiota alone could affect fat accumulation. Our findings also provide further evidence that the human gut microbiota plays an important role in the individualised response to food.