Glycation may occur either inside the body (endogenous glycation) or outside the body (exogenous glycation). Exogenous glycations and advanced glycation endproducts (AGEs) are formed when sugars are cooked with proteins or fats. Endogenous glycations occur mainly in the bloodstream to a small proportion of the absorbed simple sugars. Formation of AGEs is a complicated molecular process involving simple and more complex multistep reactions. AGEs are a very heterogeneous group of molecules.