Metabolic Barriers to Weight Gain in Patients With Anorexia Nervosa: A Young Adult Case Report

Abstract

Background: Over-proportionally high energy requirements in some patients with anorexia nervosa (AN) have been reported, but their exact origin remains unclear. Objective: To objectively measure metabolic alterations in an AN patient with high energy requirements as judged by clinical observation. Materials and Methods: We present the case of a young woman with AN (index patient, IP; 19 years, admission BMI 13.9 kg/m2). After 3 months of treatment at BMI 17.4 kg/m2, we assessed her resting energy expenditure (REE), respiratory exchange ratio (RER), diet-induced thermogenesis (DIT), seated non-exercise physical activity (NEPA in Volt by infrared sensors), and exercise activity thermogenesis (EAT) in a metabolic chamber; body composition (bioimpedance analysis), energy intake (15d-food protocol), physical activity (accelerometry) and endocrine parameters. The IP was compared for REE, RER, DIT and seated NEPA to six AN patients (AN-C) and four healthy women (HC-1), and for EAT to another six healthy women (HC-2). Results: Our IP showed high REE (110% of predicted REE according to Harris & Benedict) and high seated NEPA (47% increase over AN-C, 40% over HC-1), whereas DIT (IP: 78 vs. HC-1: 145 ± 51 kJ/180 min) and EAT (IP: 157 vs. HC-2: 235 ± 30 kJ/30 min) were low, when compared with HC. The other AN patients showed a lower REE (AN: 87 ± 2% vs. HC: 97 ± 2% predicted) at increased DIT (AN: 187 ± 91 vs. HC: 145 ± 51 kJ/180 min) when compared with HC. RER of the IP was low (IP: 0.72 vs. 0.77 in AN-C; 0.77 in HC-1 and 0.80 in HC-2). Conclusions: Complex and variable disturbances of energy metabolism might exist in a subgroup of patients with AN during refeeding, which could lead to unexpectedly high energy requirements. Future studies need to confirm the existence, and investigate the characteristics and prevalence of this subgroup. Clinical trial Registry number: NCT02087280, https://www.clinicaltrials.gov/.

Keywords: anorexia nervosa; energy metabolism; energy requirements; metabolic chamber; seated non-exercise physical activity.

Figures

Figure 1

Test protocol in the metabolic chamber. REE, Resting Energy Expenditure; DIT, Diet-induced thermogenesis; VO2 and VCO2, oxygen and carbon dioxide volumes.

Figure 2

Metabolic test results of the index patient (gray circles) and either 6 AN patients (filled circles) or 4 healthy controls (open circles). Resting (before test meal) and diet-induced energy expenditure (A: absolute, B: relative change). Exercise activity thermogenesis after a 75 g glucose drink during 30 min on a bicycle ergometer at 0.5 W/kg body weight (C: absolute, D: relative change).). PIRS: passive infrared motion sensors for assessing non-exercise physical activity inside the metabolic chamber (E: while seated; F: during exercise). Data expressed as mean ± SEM.

Figure 3

Energy intake (based on information from the patients nutritional diary) and body weight (early morning, fasted, taken weekly) during inpatient treatment.