The main function of the microbiota also known as microbiome within the gut is to protect a host from potentially pathogenic bacteria. The gut microbiota is a variety of microoranisms that inhabit the entire mammalian gastrointestinal tract. Modifications to the microbiota can result from exposure to various environmental factors, including diet, drugs, toxins and pathogens. Based on an individual’s diet, certain microorganisms within the microbiota can either be in high or low concentration. Many of these microorganisms play an essential role in certain diseases. In the gut of individuals with obesity in comparison to lean individuals there is a clear difference in microbiota composition within the gut. Two of the main microbe families found within the microbiota are Firmicutes and Bacteroidetes. In obese individuals there is a decreased amount of Bacteriodetes in comparison to lean individuals. However when obese indivduals lose weight they increase their Bacteroidetes count. This alternation in ratio of microbiota in the gut is called dysbiosis and is influenced by diet. In relation to obesity, diet also plays a role in type two diabeties because of its effects on the microbial composition of the gut. Conversely to obese individuals, for individuals with type 2 diabetes, the ratio of Bacteroidetes/Firmicutes is increased, which indicates that type 2 diabetes may not be correlated with body mass. Dysbiosis within the gut ultimately can lead to systemic inflammation, which stimulates insulin resistance, and is the indication of type 2 diabetes. Changes within the microbiota community in the gut, can also affect the intestinal barrier, which serves as a protective barrier for the intestine. The protective lining can be compromised, when there are substantial shifts in the microbiota population. This is characterized by the disease ulcerative colitis. This disease leads to an increase in susceptibility to colorectal cancer. The effects of diet on the composition of the human microbiota can be seen through an increase susceptibility to numerous diseases.