Do premorbid weight parameters predict BMI 30 years after adolescent-onset anorexia nervosa?

Purpose: To examine anthropometric predictors of BMI 30 years after the onset of adolescent AN.

Methods: A group of 51 individuals with adolescent-onset AN were identified in Sweden in 1985. Anthropometric data have been collected from birth records and school nurse charts. A group matched for gender, school and age constituted a healthy control group. Possible predictors of BMI 30 years after AN onset including ponderal index (a variable that estimates body proportionality and composition during the infancy period) and highest BMI Z score (highest BMI in childhood, adjusted for age and sex) were analyzed with linear regression and multivariate analysis.

Results: None of the five possible predictors were significantly correlated to BMI outcome 30 years after AN onset. In the control group, BMI at the 18- and 30-year follow-ups were statistically significantly predicted by ponderal index at birth (18-year follow-up: r = 0.36, p = .015; 30-year follow-up: r = 0.32, p = .034).

Conclusions: We found no statistically significant premorbid anthropometric predictors of BMI 30 years after the onset of AN. Ponderal index at birth appears to normally predict BMI outcomes in the general adult population. Having had AN during adolescence may have caused a disruption of the expected long-term BMI trajectory, resulting in a lower weight status than expected. These findings may be implemented in clinical practice to address patients' fear of exponential weight gain after recovery.