Developmental trajectories of compensatory exercise and fasting behavior across the middle school years.

Compensatory exercise and fasting behavior, in the absence of binge eating and purging, appear to be important eating disorder behaviors that are associated with dysfunction, but little is known about these behaviors in youth. We studied the trajectories of their development in non-binge eating and non-purging girls during early adolescence. Using a longitudinal design, we assessed 564 girls six times over the three years of middle school (grades 6 through 8) and developed trajectories specifying different developmental patterns in relation to the behaviors. Prior to this period, when the girls were in 5th grade (elementary school), we assessed risk factors to predict girls' subsequent trajectory group membership. Compensatory exercise trajectory groups included a non-engagement group, a group that increased in the behavior, and a group that decreased in the behavior. There were two fasting trajectory groups, one consistently engaging in the behavior and the other consistently not. Elementary school levels of depression, eating expectancies, and thinness expectancies predicted subsequent trajectory group membership. Risk for compensatory exercise and fasting should be evaluated as early as in 5th grade. Targeted interventions should focus on girls in late elementary school or middle school, as this appears to be a critical developmental and maintenance period for compensatory exercise and fasting behavior.