Self-Reported Physical Activity Energy Expenditure in Patients With Anorexia Nervosa: A Cross-Sectional Analysis at Hospital Admission From the Study of Refeeding to Optimize iNpatient Gains.

Objective: Elevated physical activity is a feature of anorexia nervosa (AN), often associated with poorer clinical outcomes. Less is known about how physical activity energy expenditure (PAEE) prior to hospital admission relates to illness severity at presentation.

Method: Secondary data analysis of the Study of Refeeding to Optimize Inpatient Gains, a randomized controlled trial comparing inpatient refeeding approaches in AN and atypical AN. Upon admission, patients self-reported: physical activity (past 7 days), Eating Disorder Examination-Questionnaire (EDE-Q), anxiety (GAD-7), depression (PHQ-A), distress tolerance (DTS), and menstrual status. Medical instability (heart rate and systolic blood pressure, orthostasis, electrolyte abnormalities) was assessed. PAEE was calculated by multiplying the activity-specific Metabolic Equivalent of Task (MET, kcal/kg/h) by the number of hours per activity; weekly METs for all activities were summed and averaged to obtain mean METs/day, then multiplied by admission body weight (kg) to obtain PAEE (kcal/d). Regressions assessed the association of PAEE and admission variables.

Results: Physical activity data were available for 91 of 116 patients (56% with AN, 95% female), with M (SD) age = 16.6 (2.5) years and %median Body Mass Index = 84.6 (11.4). Across 37 recorded activities, PAEE was 354 (319) kcal/day. Higher PAEE was associated with older age, longer duration of weight loss, higher eating restraint (EDE-Q; β = 0.17, p = 0.04), and anxiety (GAD-7; β = 0.57, p = 0.04), but not with markers of medical instability.

Discussion: Patients with high PAEE may need additional psychological support for anxiety and eating disorder cognitions during hospital admission. Further research is needed to understand how pre-admission PAEE relates to long-term recovery.

Public significance statement: Patients with anorexia nervosa (AN) and atypical AN often report increased physical activity (PA). The extent to which energy expended in PA impacts indices of illness severity in the acute phase of illness is less well understood, especially among those who are subsequently hospitalized. Findings suggest patients expending greater energy in PA prior to admission may benefit from additional support to manage higher anxiety and eating restraint while in hospital.

Trial registration: ClinicalTrials.gov identifier: NCT02488109.