Restoration of weight and nutritional status are key elements in the treatment of anorexia nervosa (AN). This review aims to describe issues related to the caloric requirements needed to gain and maintain weight for short and long-term recovery for AN inpatients and outpatients.We reviewed the literature in PubMed pertaining to nutritional restoration in AN between 1960-2012. Based on this search, several themes emerged: 1. AN eating behavior; 2. Weight restoration in AN; 3. Role of exercise and metabolism in resistance to weight gain; 3. Medical consequences of weight restoration; 4. Rate of weight gain; 5. Weight maintenance; and 6. Nutrient intake.A fair amount is known about overall caloric requirements for weight restoration and maintenance for AN. For example, starting at 30-40 kilocalories per kilogram per day (kcal/kg/day) with increases up to 70-100 kcal/kg/day can achieve a weight gain of 1-1.5 kg/week for inpatients. However, little is known about the effects of nutritional deficits on weight gain, or how to meet nutrient requirements for restoration of nutritional status.This review seeks to draw attention to the need for the development of a foundation of basic nutritional knowledge about AN so that future treatment can be evidenced-based.