Insulin, since its discovery in the 19th century until our days, has been considered as one of the biggest interests of researchers in medicine. insulin synthesis in the pancreatic islet cells is stimulated by glucose and inhibited by fasting, as glucose increases the translation of insulin mRNA and the transcription of the insulin gene. Normally, specific hormones including insulin have a central role in regulating blood glucose levels. In certain circumstances, the body cells in specific organs stop responding properly to insulin and consequently stop absorbing glucose from the bloodstream which results in high levels of glucose in the blood, that leads to increase in the insulin synthesis in the pancreatic beta cells. This is the so-called insulin resistance. One of the main causes of insulin resistance is obesity, especially abdominal obesity. There are several mechanisms for developing insulin resistance in obesity, which all together lead to decreased insulin-stimulated glucose transport and metabolism in both adipocytes and skeletal muscles, as well as an impaired suppression of hepatic glucose output. Since insulin resistance is related to several comorbidities, particularly type 2 Diabetes Mellitus, it is important to diagnose and treat patients with insulin resistance.