Myth 3: Eating a high carbohydrate diet causes insulin resistance
One of the difficulties in examining the effect of carbohydrate on insulin action is that any change in one component of the diet is accompanied by changes in other components.
As noted, as carbohydrate is increased, fat is generally decreased, and vice versa. Given that chronic consumption of foods high in fat, especially saturated fatty acids, are reported to increase insulin resistance, it is difficult to discern which macronutrient change may contribute to improvement in insulin resistance.
Long-term trials18,19 and epidemiologic studies20 have reported no harmful effects on insulin sensitivity from a high carbohydrate diet. Excessive energy intake, not carbohydrate intake, causes persons to become overweight and obese and contributes to the development of insulin resistance.21
Therefore, prevention of weight gain by appropriate energy intake, independent of the macronutrient composition, is the best approach for preventing insulin resistance. Not to be forgotten are the benefits of physical activity, which, independent of weight loss, improves insulin sensitivity.22
Bottom Line: To improve insulin sensitivity, persons with type 2 diabetes are best advised to eat a reduced energy eating pattern and participate in regular physical activity.