The current results extend past findings by showing that WS among individuals with BN predicts weight change not only over periods of a few months (Lowe et al., 2006
; Carter et al., 2008
) but over a period of 5 years. While the average weight change among individuals with BN in our sample was minimal, the trajectory of 5-year weight change differed dramatically, depending on initial WS level (). Those high in WS gained a substantial amount of weight, those with moderate WS gained a little weight, and those with the lowest WS lost a modest amount of weight. These effects were still evident when age and initial BMI were controlled.
Our findings are consistent with the literature, which concludes that on average individuals with BN experience relatively little change in BMI over time. For example, Fairburn et al. (1993)
reported that patients with BN lost a small (0.6 BMI units or about 1.5 kg) but significant amount of weight from treatment start to a one-year follow-up. In a much longer follow-up also following outpatient treatment done by Fairburn et al. (1995)
, there was a modest (and significant) increase in weight (1.6 kg over a 6-year follow-up).
Two aspects of these findings suggest that the influence of WS on weight change is powerful. One, the fact that high levels of WS predicted weight gain over such a lengthy period of time suggests that the biological and behavioral consequences of WS are persistent and that whatever tactics high-WS BN individuals use to avoid weight gain are not very effective. Two, because individuals with BN evaluate themselves largely in terms of weight and shape and abhor weight gain (Fairburn, 2008
), the weight gain observed in high-WS participants presumably occurred despite an intense fear of weight gain and fatness. Two factors that may have contributed to this weight gain are binge eating and metabolic efficiency. Past research has found a positive relationship between WS and frequency of objective binge eating in those with BN (Lowe et al., 2007
), and significant weight loss is known to produce an exaggerated reduction in metabolic rate (i.e., beyond that expected based on loss of lean tissue (Rosenbaum et al., 2008
)), which means that those higher in weight suppression would be more prone to store (as body fat) rather than oxidize energy consumed beyond energy needs.
The weight loss observed in those low in WS, unlike the weight gain of those high in WS, was presumably intentional in nature. Being at a weight that is at or near one’s highest weight ever would presumably be distressing to those with BN, which might result in weight loss efforts involving caloric restriction, purging, physical activity or some combination of these. Although volitional weight loss would generally be viewed as counter-therapeutic in the treatment of BN (Fairburn, 2008
), future research should determine how weight loss relates to treatment outcome among BN individuals low in WS.
It is possible that our findings do not reflect participants’ current level of WS so much as their inability to keep their weight at a stable level. The fact that those lowest in WS lost weight over time is consistent with this interpretation. However, WS has also predicted weight gain in normal weight college students without disordered eating (Lowe & Kral, 2006
) suggesting that weight suppression itself may be problematic.
It is notable that BMI did not predict weight change over 5 years and that BMI and WS at entrance into the study were uncorrelated. Thus absolute BMI was not informative about the extent of future weight change, but current BMI relative to highest ever BMI was predictive. The prediction of future weight change by WS indicates, in line with Russell’s (1979)
original theorizing, that therapists should assess the weight history of their bulimic patients because such information may reflect the direction and extent of future weight change, changes that could undermine therapeutic progress. For instance, despite other positive changes that may be occurring, a patient who is gaining weight may attribute it to the changes they are making, become alarmed, and drop out of treatment.
The cognitive-behavioral model of BN views over-concern with weight and shape as the “core psychopathology” of BN (Fairburn, 2008
). However, a patient’s level of weight suppression is not taken into account in the assessment or treatment of the disorder. One implication of the present results is that concern with weight should be evaluated in relation to a patient’s current body mass and especially to the difference between their current and highest-ever body weight. The greater a patient’s level of weight suppression, the more likely it is that she may be caught in a “biobehavioral bind” (Butryn et al., 2006
) from which she cannot extricate herself. That is, a (realistic) fear of weight gain may lead to vigorous dieting, which could exacerbate binge eating and purging. The way out of this dilemma is not clear, but it could involve preparing the patient to accept the possibility that some weight gain may occur during treatment and in fact may be helpful in reducing the pattern of restricting, binge eating and purging that comprise BN. Although CBT for BN does inform patients that their weight may change during treatment (Fairburn, 2008
), the likelihood and direction of future weight change based on a patient’s weight suppression level is not considered.
Two qualifications need to be taken into account when interpreting the present results. First, the construct of current dieting is different from the construct of WS (Lowe, 1993
). In fact, current dieting among those with bulimia nervosa has been found to be associated with reduced
levels of binge eating (Lowe et al., 1998
; Lowe et al., 2007
) whereas WS was found to be positively related to binge eating frequency (Lowe et al., 2007
). Second, the consequences of WS in bulimia nervosa appear to be different than in obesity. Studies from the National Weight Control Registry indicate that previously obese individuals who lose substantial weight and keep it off do not appear to be more susceptible to disinhibited or binge eating (Wing & Hill, 2001
Strengths of this study include the use of structured diagnostic interviews, frequent assessments of body weight, and the long-term follow-up. A possible limitation of the study is that follow-up weights were collected via self-report, though this concern is mitigated somewhat because there was almost no discrepancy between the average of measured and self-reported weights at baseline. The results are based on women with BN who were willing to join the study and report repeatedly on their clinical status over many years. The generalizability of the results to other populations with BN cannot be assumed.
In conclusion, the present study adds to several others indicating that bulimic patients on average maintain body weights well below their highest historical weights and that such weight suppression may contribute to weight gain and help perpetuate their eating disorder. Future research should explore the therapeutic implications of treating BN patients with elevated levels of weight suppression.