Diet, Gut Microbiota and Obesity

Abstract

Mini Review including fermenting unused energy substrates, training the immune system, maintaining epithelial integrity, regulating gut development, and preventing the invasion of pathogenic bacteria [4,5]. Recent studies based on 16S ribosomal-RNA gene sequencing and metagenomic analysis have started to explore the species diversity of gut microbiota within and between individuals [6,7]. It is estimated that about 1000 species can colonize the human gut. Although there is a big range of variation in the species level from different individuals, one recent study showed that the gut microbiota of most individuals can be classified into one of three clusters ('enterotypes') based on the three dominant bacterial genera, Bacteroides, Prevotella, and Ruminococcus [8]. The composition of the gut microbiota is determined and influenced by a number of factors, such as genetics, age, geographic origin, diet and the use of antibiotics [4,5]. One study has compared bacterial species of fecal samples from 531 individuals of different ages (0-70 years) and geographic origins (three populations from US and Malawi) [9]. It was found that the diversity of the gut microbiota within individuals is much higher in adults than in children, but that the interpersonal differences are significantly higher in children. The composition of the bacterial community converges towards an adult-like microbiota by the end of the first 3-5 years of life. These features are shared in all three populations. Gut Microbiota and Obesity Studies from the past decade have provided strong evidence of the association between obesity and gut microbiota [10-14]. For example, by transplanting human whole fecal microbiota from obese (Ob) and lean (Ln) twins to germ free mice, one recent study showed that the gut microbiota modulates host metabolism to regulate body mass [13]. Mice that received fecal microbiota from the Ob twins had increased total and fat mass and showed obesity-associated metabolic disorders, phenotypes that were not observed in mice receiving fecal microbiota from Abstract Increasing evidence suggests that alteration of gut microbiota ('dysbiosis') can lead to a number of diseases, including obesity, which affects a large population in the world and is now a global health issue. The mechanisms of gut microbiota-mediated obesity are just being explored and characterized in recent years. It has been suggested that dysbiosis of gut microbiota contributes to obesity development mainly in three ways: affecting energy harvest, altering host gene expression, and triggering chronic inflammation. Among the factors that determine and influence gut microbiota composition, diet is one of the best characterized in human and animal studies, and has been long linked with weight gain or loss. In this review, we will discuss recent advances of mechanisms through which gut microbiota dysbiosis leads to obesity. We will further discuss the underlying causes of obesity-related gut microbiota, highlighting dietary effects.