A dietary manager is a trained food services professional who is charged with maintaining cost/profit objectives, purchasing foods and services for the department and supervising staff.. Dietary managers are trained to understand the basic nutritional needs of clients and work in partnership with dietitians, who offer specialized nutritional expertise. The CDM certified dietary manager designation is an advanced professional credential awarded to dietary managers who have completed specific course work, have passed the national credentialing exams (including a sanitation and safety exam) and have applied for certification.