Type 2 diabetes is a condition which affects many individuals around the world, resulting in elevated blood sugar levels. There are many risk factors associated with diabetes, such as high fat and sugar intake, obesity, and a lack of exercise; however, the mechanism that causes it has not been identified. Research has found that people with type 2 diabetes have an altered gut microbiome, a collection of trillions of microorganisms living along the gastrointestinal tract, compared to healthy individuals. The gut microbiome is currently a popular area of research, and recent studies have found it to influence the immune system, heart, and brain.

The purpose of this study was to determine if a high fat diet, one of the risk factors of type 2 diabetes, causes the gut dysbiosis seen in people with type 2 diabetes. 3 different species of bacteria: L. plantarum, S. mutans, and S. epidermidis, were exposed to oleic acid, linoleic acid, and palmitic acid in concentrations resembling both the recommended daily allowances and a high fat diet. All of the fats were "digested” using an in vitro digestion procedure to simulate human gastric and intestinal digestion.

Then, the bacteria were exposed to the different fats for 6 hours, during which bacterial growth was measured using a spectrophotometer. The raw spectrophotometer values were normalized to represent percent growth compared to the average of the control values at 6 hours. Total growth was calculated, and T-tests were performed on the data to determine statistical significance between experimental groups.

Compared to a regular diet, a high fat diet of oleic acid, a monounsaturated fat, caused all 3 bacteria to grow 469%-2004% more. Exposure to palmitic acid, a saturated fat, brought about similar results, as a high fat diet caused a significant increase in bacterial growth, with a range of 149%-891% between all 3 bacteria. Of all 3 bacteria exposed to linoleic acid, a polyunsaturated fat, only S. mutans showed a significant increase in growth when exposed to a high fat diet compared to a regular diet, growing 293% more than with a regular diet.

In general, each species of bacteria grew more during the 6-hour period when exposed to higher concentrations of each fat. This trend is in agreement with existing literature, describing that L. planta rum, S. mutans, and S. epidermidis are all found in significantly higher concentrations in the gut microbiomes of type 2 diabetics. This study suggests a connection between gut dysbiosis caused by a high fat diet and the onset of type 2 diabetes, and with further research, it could present a possible cause of type 2 diabetes relating to an altered gut microbiome.