Rigorous exercise to control weight and/or shape and to avoid negative affect has been proposed as significant in the etiology, development and maintenance of eating disorders (EDs), resulting in more severe and enduring pathology. However, few studies have investigated compulsive exercise (CE) among adolescents with EDs.

To study the longitudinal relationship between EDs and CE in adolescents.

Aims to investigate if adolescent ED patients show a similar relation between EDs and CE as previous research has found in adults.

A total of 3116 girls and 139 boys from a nationwide clinical EDs database were investigated on CE prevalence and frequency in relation to ED diagnosis, psychiatric symptoms, associated features and outcome. Denial of illness in self-ratings was adjusted for.

Adjusted CE prevalence in girls was 44%; with highest prevalence in bulimia nervosa. Average CE frequency was 3.9 times/week (SD=2.6). Those with CE scored significantly higher than non-CE on total ED severity, dietary restriction and negative perfectionism (P<0.001). There were only minor differences between CE and non-CE patients on emotional distress, hyperactivity, suicidality and self-esteem. Among boys, adjusted CE prevalence was 38%, and only total ED severity was significantly related to CE (P<0.05). Initial CE did not impact prognosis, yet cessation of CE during 1-year follow-up was associated with ED remission.

CE is a common clinical feature in adolescents with EDs, as previously found in adults. CE had less detrimental impact on EDs than predicted and cessation was associated with better outcome.