A prospective test of the relation between weight change and risk for bulimia nervosa

Little is known about the relation between relative body weight and the development of BN. Russell1, in his classic paper that first formally identified this syndrome, noted that BN was “an ominous variant of anorexia” and that these patients, though typically presenting with “unremarkable” body weights, weighed significantly more prior to the development of their eating disorder. Others2-4 have presented evidence that individuals with BN are significantly weight-suppressed, that is, their current weight tends to be substantially below their retrospectively reported highest weight ever relative to controls. Because individuals with BN are typically in the normal weight range, this implies that many patients with BN were somewhat overweight at their previous highest weight. Similarly, Fairburn et al.5 and Yates6 report that individuals with BN retrospectively reported a higher premorbid body mass than healthy controls and that there was a greater history of overweight in first-degree relatives of BN individuals. On the other hand, the normal weight status of most individuals with BN also conceals a weight history that involved weighing significantly less than they currently weigh. Garner and Fairburn3 reviewed evidence suggesting that most individuals with BN lose a great deal of weight in the process of developing their disorder, with roughly a third reaching body weights characteristic of anorexia nervosa before gaining weight and transitioning to BN.7 Further, case study and non-experimental research suggests that significant weight loss precedes – and presumably spurs the development of – binge eating.8-10 In sum, many individuals with BN report a history of both higher and lower body weights relative to their weights when they come to the attention of researchers or clinicians. However, little is known about whether weight gain or weight loss increases risk for the development of BN. A fundamental weakness in existing studies of the possible role of weight history in BN is that the relevant data are collected retrospectively. Such retrospective reports are often inaccurate because of natural forgetting that happens over long periods of time, because memories are influenced by current mood state and subsequent events, people tend to distort memories in a more socially desirable direction, people may reinvent the past to suit their current needs and circumstances, and people tend to remember events as happening earlier than they actually did.(e.g., 11,12) It would be preferable to examine the relation of weight change to the development of bulimic pathology prospectively by (a) examining bulimic symptom frequency before and after individuals have gained or lost a significant amount of weight and (b) by identifying individuals who develop bulimic pathology and determining whether weight loss or weight gain preceded the emergence of this pathology relative to a similar group that did not develop bulimic pathology. No prospective study has tested whether significant weight loss or weight gain increases risk for future development of bulimic pathology or tested whether those who develop bulimic pathology experience accelerated weight loss or weight gain prior to the development of this pathology. Because self-reported weight and height, whether collected contemporaneously or retrospectively, have questionable accuracy, (c.f., 13) it would be preferable to rely on directly measured height and weight. This study prospectively examined the relation between weight change and onset of threshold or subthreshold BN in two different ways. The first aim was to identify participants in this data set who experienced a substantial weight loss or weight gain during the 8 years and determine if either weight change pattern was associated with increased risk for onset of threshold/subthreshold BN in the year during or soon after the weight change occurred relative to a control group who was weight stable across the 8 years. The second aim was to test whether individuals who showed onset of threshold/subthreshold BN evidence a history of significant weight loss or weight gain previous to onset of the eating disorder relative to those who remained free of this eating disorder.