The gut microbiota is associated with metabolic disorders such as obesity and diabetes mellitus. A study from the National Food Institute demonstrated that mice that received gut bacteria transplants from overweight humans gain more weight than mice transplanted with gut bacteria from normal weight humans, even when the mice are fed the same diet.
Evidence shows that the gut microbiota helps to harvest energy and increase host fat storage. Human studies and animal models have been used to demonstrate that the gut microbiota is altered in obesity. One of the hallmarks of obesity and obesity-related pathologies is the occurrence of chronic low-grade inflammation. This ongoing low-grade inflammation is sustained by bacterial substances (LPS, endotoxin) which are found at low concentrations in healthy individuals but reach high concentrations in individuals with obesity, a condition called metabolic endotoxemia. One mechanisms linking obesity and metabolic endotoxemia which has been proposed is that during consumption of a high-fat diet, the gut microbiome is modified, which leads to increases in gut permeability and in the systemic levels of bacterial products such as LPS. LPS fuels the ongoing inflammatory processes which supports the metabolic imbalance.