The gut microbiota and its products: Establishing causal relationships with obesity related outcomes.

Gut microorganisms not only participate in the metabolism of carbohydrate, lipids, protein, and polypeptides in the intestine but also directly affect the metabolic phenotypes of the host. Although many studies have described the apparent effects of gut microbiota on human health, the development of metagenomics and culturomics in the past decade has generated a large amount of evidence suggesting a causal relationship between gut microbiota and obesity. The interaction between the gut microbiota and host is realized by microbial metabolites with multiple biological functions. We concentrated here on several representative beneficial species connected with obesity as well as the mechanisms, with particular emphasis on microbiota-dependent metabolites. Finally, we consider the potential clinical significance of these relationships to fuel the conception and realization of novel therapeutic and preventive strategies.