Weight status and weight-control exercise in adolescents: A longitudinal population-based study.

Objective: Exercise is a transdiagnostic clinical feature of eating disorders, but consensus is lacking as to what constitutes, and gives rise to, excessive exercise motivated by weight control. Using a longitudinal cohort study, we aimed to describe population-level prevalence rates of varying levels of weight-control exercise and examine gender and weight status (overweight or obesity; OVOB) as cross-sectional determinants of weight-control exercise in 14-15-year-old adolescents. We then evaluated the association of OVOB at 10-11 years with weight-control exercise at 14-15 years.

Methods: The sample comprised 6329 adolescents from the Longitudinal Study of Australian Children (LSAC). Weight and height were measured in early adolescence (aged 10-11) and in mid-adolescence (aged 14-15). Participants reported weight-control exercise using the Branched Eating Disorders Test at 14-15 years.

Results: In mid-adolescence, the estimated population prevalence for any weight-control exercise was 49 % (55 % in females). For girls, moderate levels of exercise were most prevalent, and low levels for boys. For all levels except for the very lowest, boys with (vs. without) OVOB history (10-11 years) had about twice the odds of endorsing every level of weight-control exercise. Patterns among girls were similar, though lower in magnitude (∼1.5 times).

Conclusions: For both girls and boys, across most exercise levels, rates of weight-control exercise were greatest for those with OVOB; for the highest exercise level, effects were strongest for boys with OVOB. To accurately identify at-risk adolescents, our results provide preliminary support for a fluid definition of excessive weight-control exercise, dependent on gender and weight status.