Nutritionists are individuals who provide food and preventative nutrition to individuals. Nutritionists have to undergo years of training in order to represent themselves as a professional. Typically there is a certification the person must have from a vocational school before they can begin to serve customers. In the United States nutritionists need a RD or a registered dietician certification.
Since not all states have the same laws regarding nutritionists there is a directory a person can check to ensure they have a licensed or qualifying nutritionist to work for them. Nutritionists will treat and prevent disease relating to improper diets. They can also do academic research to determine what foods are better for a person. Since not all humans are the same a plan for each person is needed.