Nutritional rehabilitation in anorexia nervosa: review of the literature and implications for treatment

Abstract

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.

Figure 1

Restricting-type anorexia nervosa (R-AN) patients need more kilocalories (kcal) than binge-purging-type AN (BP-AN) patients to gain the same amount of weight. While individuals with restricting-type and binge-purging-type AN consume similar kcal per kilogram (kg) per day, those with restricting- type AN gain weight more slowly in terms of % average body weight (% ABW) (Kaye et al., unpublished data).

Figure 2

Percent average body weight (% ABW) and kilocalories/kilogram per day (kcal/kg/day) in a typical course for a restricting-type anorexia nervosa individual who entered at 70% ABW. Individuals with anorexia nervosa tend to require escalating caloric intake in order to maintain a 1 to 1.5 kg/week weight gain during hospitalization (Kaye et al., unpublished data).

Figure 3

Relationship between physical activity counts per day and the amount of kilocalories needed to gain each kilogram (kg) of body weight. Exercise contributes to approximately a threefold range of calories to gain 1 kg of body weight (Kaye et al., 1988 [45], republished with permission).

Figure 4

Mean 24-hour core body temperature in individuals with anorexia nervosa (AN) at stages of weight restoration. Increased caloric consumption is associated with an increase in core body temperature. At peak caloric intake (i.e. stage 3) AN patients lose the normal night time drop in body temperature; their temperature at night is elevated and they report being diaphoretic at night when asleep (Kaye et al., unpublished data).

Figure 5

Comparison of daily caloric requirements. In the month after restoration of a healthy body weight, both restricting anorexics (R-AN) and binge-purging anorexics (BP-AN) remain energy inefficient when compared to individuals studied after long-term (>1 year) weight restoration or healthy control women (CW) ([13,16,18] original figure, no permission required).