Nutritionist. A nutritionist, or "registered dietitian" is educated to assist in the treatment of various medical conditions through diet manipulation (macro and micronutrients). They can assist in the treatment of diabetes, high blood pressure, high cholesterol and digestive problems, just to name a few. They attend five years of college and often have Master's degrees as well.
To advice on nutriti. The job of nutritionist is to advice about food and nutrition and its impact on a persons health.