Within-subject weight variability in bulimia nervosa: Correlates and consequences

Objective The oscillations between binge eating, purging, and dieting in bulimia nervosa (BN) may produce substantial within-subject weight variability. Although weight variability has been predictive of eating- and weight-related variables in community samples, it has not been empirically examined in eating disorders. The current study examined cross-sectional and prospective associations between weight variability and BN pathology. Method Four weights were collected over an average of 42.02 days, and weight variability was calculated as the root mean square error around each individual's weight trajectory regression line. Linear regressions were performed to examine the association between weight variability and eating disorder psychopathology, cross-sectionally at baseline and prospectively at 6-month follow-up, adjusting for baseline BMI. Results Weight variability was cross-sectionally associated with eating pathology, but these relationships became non-significant after adjusting for BMI. However, at 6-month follow-up, greater baseline weight variability predicted increases in body dissatisfaction, shape and weight concerns, and global eating pathology, even after adjusting for baseline BMI. Discussion These findings demonstrate, for the first time, that within-subject weight variability predicts greater eating disorder pathology over time in BN. The results add to evidence that weight history variables contribute to BN psychopathology above and beyond well-documented psychological dysfunction in BN.