Nutrition & Dietics Dietetics involves using nutritional knowledge to help individual patients. It's mainly based in hospitals, where it focuses on using diet to treat and manage illness.The taking in and use of food and other nourishing material by the body. Nutrition is a 3-part process. First, food or drink is consumed. Second, the body breaks down the food or drink into nutrients. Third, the nutrients travel through the bloodstream to different parts of the body where they are used as "fuel" and for many other purposes. To give the body proper nutrition, a person has to eat and drink enough of the foods that contain key nutrients.