Food is a medicine that has been used to assist health for hundreds of years.    Food management and control is about discovering which food types and quantities are optimum to improve and maintain health.

Much of immune system is located in, or around the gut because the most likely source of a foreign substance entering the body is through the digestive tract and into the blood stream.   The relationship between certain foods and health is well established (eg coeliac) despite not fully understanding the complex relationship between the digestive, nervous & immune systems.
 
Food deprivation diets do not work.  These diets are based on a sense of guilt and/or losing control.  Whether the diet is for health benefits or for weight reduction, history shows how difficult it is to maintain a food deprivation diet for a significant period of time.