The gut microbiota in human energy homeostasis and obesity

• This manuscript provides an overview of what is known about the role of the gut microbiota in rodent and human energy homeostasis.
• This manuscript reviews the differences between humans and rodents that may affect the ability to extrapolate conclusions from one order of mammals to the other.
• This manuscript suggests future directions of research into the human microbiota that are informed by rodent studies.

Numerous studies of rodents suggest that the gut microbiota populations are sensitive to genetic and environmental influences, and can produce or influence afferent signals that directly or indirectly impinge on energy homeostatic systems affecting both energy balance (weight gain or loss) and energy stores. Fecal transplants from obese and lean human, and from mouse donors to gnotobiotic mice, result in adoption of the donor somatotype by the formerly germ-free rodents. Thus, the microbiota is certainly implicated in the development of obesity, adiposity-related comorbidities, and the response to interventions designed to achieve sustained weight reduction in mice. More studies are needed to determine whether the microbiota plays a similarly potent role in human body-weight regulation and obesity.