Use of Indirect Calorimetry in Nutritional Rehabilitation of Adolescents With Anorexia Nervosa

Abstract

LEARNING OUTCOME: To describe how indirect calorimetry can be used to assess the energy needs and monitor the progress of nutritional rehabilitation in adolescents with anorexia nervosa. Predictive equations are not useful in assessing energy needs of malnourished patients with anorexia nervosa. They are often admitted with significant weight loss and reduced resting energy expenditure (REE) in response to semistarvation. During the first few weeks of refeeding and rapid weight gain, REE is significantly increased and remains higher than predicted values until the patients are weight recovered. In order to prescribe energy intake required for weight gain accurately, it is necessary to actually measure REE levels during nutritional rehabilitation. In our institution, all admitted adolescents with anorexia nervosa have their REE assessed by indirect calorimetry within the first three days of admission and every two weeks thereafter until they are completely nutritionally rehabilitated. Preliminary results showed that at admission, mean REE value (n=10, 11–15 years old) was 79±11% (range 61–97%) of predicted values using Schofields formulas. After refeeding REE rose to peak ranging from 120 to 156% of predicted values. The rate of increase in REE varied among patients and could only be explained partially by weight gain. It took about 6–8 weeks before the REE values returned to normal. Patients were generally completely rehabilitated (as measured by acceptable weight and body cell mass) when their REE values were within 100±10% of the predicted values. Both lower and higher than predicted normal REE values can thus be used as an indicator for incomplete nutritional rehabilitation. This results confirmed that at different stages of nutritional rehabilitation, patients had different energy needs for weight gain and weight maintenance, and energy requirements should be based on individual REE measurements.