Persons with IR have a reduced capacity to burn carbohydrate as a fuel both during exercise and when at rest, or to store it as glycogen. As a result when they eat a carbohydrate-rich diet, those with IR will store most of the excess carbohydrate as fat, even if they perform prodigious amounts of exercise (in an attempt to burn off the excess carbohydrate). Some even argue that storing carbohydrate as fat is the way the human body is designed to cope with a toxic chemical (glucose), which until the Agricultural Revolution was not a major component of the human diet.
