Most diets out there are balanced and hypocaloric, meaning that you consume a proportionate amount of calories from carb, fats, and proteins respectively, while reducing the total calories consumed.
By this method, you are eating the same macronutrients, just reducing total energy intake; this does not change your metabolic state, which is a problem if you have something like infertility due to hyperinsulinemia or insulin resistance.
If the dieter had a dysfunctional pancreas (i.e. hyperinsulinemia / insulin resistant) prior to dieting and the diet did not address this issue, then they will still be in this condition at the conclusion of their diet and will be predisposed to regain.
With the IP protocol, we “reset” the pancreas. This addresses the above mentioned problems, regulates menstruation and reverses weight-related infertility. In fact, so many women experience increased fertility that you are required to use a barrier contraceptive method while on the protocol, if you do not desire pregnancy.