Will I get fat? 22-year weight trajectories of individuals with eating disorders.

OBJECTIVE: For some, fat phobia or fear of uncontrollable weight gain is diagnostic of eating disorders, often inhibiting treatment engagement and predicting symptom relapse. Prior research has reported weight changes at infrequent or long intervals, but rate, shape, and magnitude of long-term changes remain unknown. Our study examined 22-year longitudinal trajectories of body mass index (BMI) in women with anorexia nervosa (AN) and bulimia nervosa (BN).

METHOD: Participants were followed over 10 years (N = 225) and at 22-year follow-up (N = 175). Using latent growth curves, we examined: (1) shape and rate of intra-individual BMI change over 10 years; (2) predictors of BMI change over 10 years, (3) 22-year BMI outcomes; and (4) BMI changes over 10 years as predictors of 22-year BMI.

RESULTS: The best-fitting model captured overall intra-individual rates of BMI change in three intervals, showing moderate rate of BMI increase from intake to year 2, modest increase from year 2 to 5, and plateau from year 5 to 10. At 22 years, 14% were underweight, 69% were normal weight, and only 17% were overweight or obese. Greater increases from intake to year 2 predicted higher BMI at 22 years (β = 0.43, p < 0.01) and were predicted by intake diagnosis of AN-restricting (β = 0.31, p < 0.01) or AN-binge eating/purging (β = 0.29, p < 0.01).

DISCUSSION: BMI increased most rapidly during earlier years of the study for those with lower weight at study intake (i. e., AN) and plateaued over time, settling in the normal range for most. Psychoeducation about expected BMI trajectory may challenge patients' long-term fat phobic predictions.