The Complex Interplay of Diet and the Gut Microbiome Influences Human Health

In a controlled feeding study in people, researchers found that a diet designed to nourish the gut microbiome led to altered microbial composition, diversity, and function; changes in people’s hormones; and improved energy balance (i.e., the relation of calorie intake to calories used or excreted). Gut microbes have long been associated with body weight and metabolism through their ability to harvest energy from food. However, prior studies in people have lacked the precision necessary for a comprehensive evaluation of the contributions of the gut microbiome to energy balance. Thus, in this randomized study, the researchers developed a diet intervention to address these critical knowledge gaps.

Employing a microbiome enhancer diet (MBD) designed to deliver more fiber and other dietary sustenance to the gut, the researchers gave 17 healthy, weight-stable men and women either the MBD or a standard, Western diet (WD) with less fiber and more processed foods for approximately 3 weeks. This was followed by the other diet for the same amount of time. Using specialized laboratory techniques in a metabolic ward, the researchers measured energy intake, energy expenditure, and energy output (fecal and urinary) in each participant on each diet and made “within-participant” comparisons. They found that, compared to the WD, the MBD led to an additional 116 calories lost in feces daily, meaning less energy available for the person to metabolize and improved energy balance. When they explored compositional and functional changes in the microbiome, they discovered that the MBD led to an altered diversity of microbes and to an increase in microbes with an ability to break down nutrients, such as fiber, more efficiently to produce beneficial molecules compared to the WD. In addition, the researchers uncovered a small, but measurable, decrease in body fat stores on the MBD. Lastly, the MBD was associated with a notable increase in circulating hormones that are known to promote a feeling of fullness.

Taken together, these results suggest that an intentional remodeling of the gut microbiome through provision of adequate dietary fiber and minimally processed foods can modulate human energy balance. Future research on the complex interplay of diet and the gut microbiome could lead to personalized nutrition approaches.