Interactions between gut microbiota, food and the obese host

•Gut microbiota contribute to the modulation of body weight and immune responses.•Intake of probiotics and prebiotics to control adiposity has given promising results.•The mechanisms relating gut microbiota and obesity need to be unraveled.

The recent research focus on the human microbiota has provided data which suggests that the composition of the gut microbiota can play an important role in the modulation of body weight and of related mucosal and systemic immune responses. However, recent results from human and animal studies have raised the debate about whether specific microbial groups play a causative role in obesity or if the gut microbiota is modulated in response to diet or the obese state itself. Studies targeting selective alterations in the gut microbiota to control weight gain through the intake of probiotics and/or prebiotics or modulating undesirable populations through the use of antimicrobials or transplantation of faecal microbiota have provided promising results. Nonetheless, further placebo-controlled, double blind human studies are still required. Likewise, while it is now well accepted that obesity is followed by a low grade inflammatory response, more research studies are needed to unravel the mechanisms that would explain how different microbiota profiles affect the mucosal and systemic immune responsiveness, the intestinal barrier function and the development of adiposity.