Insulin resistance occurs when cells of the body become less sensitive to the effects of insulin. Therefore, sugar that's circulating in the blood doesn't enter the cells easily. This leads to a build up of sugar in the blood stream. When insulin resistance develops, the body tries to compensate by producing more insulin. Initially this may be sufficient to maintain normal blood sugar levels. However over time the ability of the pancreas to produces more insulin wanes, leading to high blood glucose levels. 

Insulin resistance in combination with decreased insulin production result in the development of Type 2 diabetes.

Factors that contribute to insulin resistance include:

• older age
  
• sedentary lifestyle
  
• being overweight or obese
  
• other hormonal conditions such as Polycystic Ovarian Syndrome.