Glucose-dependent insulinotropic peptide (GIP) is an incretin secreted in the intestine by K cells and is released mainly by a nutritional stimulus mediated by fat and carbohydrate intake. This incretin is implicated in the development of pathologies such as diabetes and obesity, which are among the leading causes of death worldwide. The aim of this study was to review studies reporting the modulation of incretin gene expression and its function in both normal and pathological conditions such as IIDM and obesity. The studies are available in the PUBMED, SCIENCEDIRECT, MEDLINE databases. Fifty-one articles demonstrating strong evidence on the topic were selected. The evidence reports that GIP in normal states has the main function of promoting insulin secretion and redistribution of adipose tissue. In type 2 diabetes, however, its function was found to be null given the low activity of its receptor on beta cells. In obesity, it was observed that it can contribute to the pro-inflammatory state through the activation of cytokines.