The gut microbiota plays a pivotal role in the interplay between physiological well-being and pathobiological conditions. Manipulation of the microbiota has become an exciting space for the development of therapeutic products for several diseases, no less obesity.
Metabolic products of gut microbiota, such as short-chain fatty acids have known roles in host metabolism, lipogenesis and gluconeogenesis through incretin and hormonal signalling, and direct nervous system modulation. By manipulating the microbiome, and consequently their metabolic products, there is the potential to modulate health and decrease adiposity. This is possible by several routes, including diet, probiotics and prebiotics. Additionally, faecal microbiota transplantation (FMT) of donor material into a recipient is a promising method of modulating the microbiome. Animal studies of FMT support FMT's usefulness in eliciting weight loss when using lean human donors to mouse model recipients. In adolescents, FMT has led to reduced adiposity but not weight loss per se, supporting the concept of human-to-human transfer. However, the utility of FMT in treating obesity in adults remains unsubstantiated.
Varying results from FMT trials in obesity have been compounded by inconsistent methods of delivery, differing doses of FMT materials and a lack of adequate selection of donor material to suit the recipient population (either to effect changes to the microbiota or metabolomic landscape). While a super donor concept has been proposed for Inflammatory Bowel Disease (IBD), it is unclear if this is relevant and possible in obesity. Moreover, many confounding factors have not been adequately addressed, particularly the influence of dietary changes, both short and long-term, on engraftment and maintenance of the implanted microbiome.
With the rapid progress in sequencing methods, AI and multi-omics characterisation of the microbiome environments of obesity and health, we are starting to see a path towards the use of FMT in the treatment of adult obesity.