Other than the genes you inherited, there are two primary causes of insulin resistance:
1) A long-term diet that has been high in carbohydrates and
2) Nutritional deficiencies.
When you eat, your body breaks the food down into sugar (glucose), which then enters your blood stream. When the glucose in the blood increases, the body produces insulin to push the sugar out of your bloodstream and into the cells where it can be used. When insulin is doing its job, it will keep your blood sugar in normal range.
The human body evolved eating meat, fat and high fiber vegetables, with some roots and tubers.
Eight thousand years ago the “agricultural revolution” took place, with man learning how to domesticate grain. Virtually overnight, man became dependant upon carbohydrates as the main source of food. Archeologists point to that exact time period that the average height of man drops by two inches and all of the degenerative diseases we have today became prevalent in the society of that time.
Carbohydrates are simply long chains of sugar molecules hooked end-to-end. When a person eats carbohydrates their normal digestive process breaks up these chains into the individual sugar molecules, and they pass right through the intestinal wall into the bloodstream, and load up the bloodstream with sugar.
If this happened every once in a while it would not be a problem. But as diets today are so high in carbohydrates, people have a constant high level of sugar pouring into their bloodstream year after year.
This requires the body to continuously produce high levels of insulin to keep that sugar level down. (Remember, Insulins job is to push sugar out of the bloodstream into the cells where it is used for energy.)
Eventually the cells in the body become insensitive to the effects of the insulin. There are little doors to the cell (called cell receptors) where insulin pushes the glucose into the cell. When these cell receptors become insensitive to the insulin, insulin cannot open these doors. This is called insulin resistance.
To handle this problem the body begins to produce even higher levels of insulin. This continues until their pancreas (where insulin is made) reaches the maximum amount of insulin it can produce, and when the insulin resistance of the cells increases again, the blood sugar begins to rise out of control.
The result is type 2 diabetes. Type 2 diabetes is actually an extreme case of insulin resistance.
When the body has become insulin resistant, the body needs a low carb pre diabetes diet to maintain normal bloods sugars and needs specific nutrients supplements to re-sensitize the cell receptors of the body to the insulin the body is making.