An Investigation of Weight Suppression in a Population-Based Sample of Female Twins

Weight suppression (WS), defined as the discrepancy between one’s highest adult and current weight, is a relatively understudied concept in the area of eating disorders. It was first highlighted in Lowe’s [1] three-factor model of dieting behavior, which included frequency of dieting and overeating, current dieting, and WS. To date, this construct has been investigated primarily among clinical samples, and evidence suggests that WS negatively impacts the course and treatment of eating disorders [e.g., 2]. However, given the rapid increases in rates of overweight and obesity in the U.S. [3–4], it is possible that the ability to maintain weight loss could be advantageous among subsamples of the general population. The following sections briefly review studies of WS and eating-and weight-related constructs among eating disordered and non-eating disordered samples. Restraint theory posits that dietary restraint leads to subsequent overeating [5–6]. However, some have argued that restraint theory does not distinguish between chronic and acute dieting [1]. That is, while acute dieting may increase risk for overeating (including binge eating), chronic dieting may be advantageous for sustaining healthy weight loss. Data suggest that individuals who successfully maintain weight loss in the long term are able to consciously control their dietary intake. For example, participants in the National Weight Control Registry, who have lost an average of 33 kg and maintained this weight loss for more than five years, report fairly high levels of cognitive restraint [7]. Notably, these levels are lower than those of eating disorder patients [7]. Experimental studies suggest that individuals who have lost weight successfully and maintained that loss (i.e., weight suppressors) have adapted their appetitive reactions in a way that facilitates their ability to control weight (e.g., reduced preference for sweets [8]). Thus, the construct of WS may behave differently among individuals with and without eating disorders. Most investigations have demonstrated the negative effects of WS on eating disorders and related constructs. In addition, it has been hypothesized that WS might be particularly relevant to bulimia nervosa (BN), as individuals with this disorder often enter treatment at weights substantially below their highest adult weights. Specifically, in two samples of BN patients in a low-normal weight range, Garner and Fairburn [9] found that one-third and one-half, respectively, had previously been at least 15% overweight. Further, WS was found to be a significant predictor of weight gain among individuals receiving inpatient treatment for BN [10]. WS was also positively associated with binge eating frequency in a sample of women with BN [11]. Evidence further suggests that WS can impact the course of this disorder [2, 11]. For example, Butryn et al. [2] found that WS predicted attrition from BN treatment as well as poor outcomes (i.e., inability to achieve abstinence from bingeing and purging) among treatment completers. Taken together, these results suggest that WS may contribute to the development and maintenance of eating disorders, particularly BN. In addition to these investigations of WS in samples of patients with eating disorders [2, 10, 11], one recent study included non-treatment seeking college freshmen [12]. Lowe, Annunziato et al. [12] found that WS and a history of dieting for weight loss predicted weight gain. However, restraint, disinhibition, and emotional eating were not associated with weight gain in this sample. The authors noted that these results provided further support for WS and restraint as distinct constructs; further, they argued that WS appears to be a robust predictor of future weight gain. These studies provide important information regarding the WS construct; however results from treatment-seeking and college samples may not be applicable to the general population of adults. Although WS has been associated with eating disorder-related traits and weight gain among these groups, eating disordered and college samples might be particularly vulnerable to both more severe eating disorder symptomatology as well as greater weight gain than the general population [12]. Thus, the current study investigated associations among WS and eating disorder-related variables in a population-based sample of female twins, to determine whether these relationships differ for individuals reporting binge eating and loss of control (BE+LOC) vs. those reporting no binge eating (NBE). We chose to examine this form of disordered eating in our population-based sample, as evidence suggests that individuals manifesting subthreshold levels of binge eating report levels of distress comparable to those with binge eating disorder (e.g., [13]). The current study also estimated genetic and environmental influences on WS. Twin samples are useful for such analyses, as including both monozygotic (MZ) and dizygotic (DZ) twins in a structural equation model allows the variance of a given trait to be partitioned into additive genetic (A), common environmental (i.e., that which is shared among twin pairs; C), and unique environmental (i.e., that which is not shared among twin pairs; E) influences [14]. There are several reasons why twin research could provide insight into WS and related constructs. First, body mass index (BMI) is strongly influenced by genetic factors (e.g., approximately 50–90% of variance in BMI is attributable to additive genetic effects [15]). Second, twin studies of eating disorders have found that AN, BN, and related behaviors (e.g., binge eating and vomiting) are moderately heritable (for a review, see Bulik, et al. [16]). However, twin studies have also indicated that specific disordered eating related behaviors and attitudes are differentially influenced by genetic and environmental factors. For example, Neale et al. [17] found that disinhibited eating was most strongly influenced by additive genetic factors. However, restraint was more strongly influenced by common environmental factors. Similarly, the undue influence of weight on self-evaluation has been found to be more strongly influenced by environmental, rather than genetic, factors [18]. Thus, it is unclear to what degree genetic and environmental factors might influence liability to the specific construct of WS. In sum, the current study investigated WS among NBE and BE+LOC women in two ways. Regression models investigating relations between WS and eating disorder-related constructs (body dissatisfaction, drive for thinness, Restraint, Disinhibition, Hunger, and time spent dieting before and after age 18) were conducted separately in these two subsamples. We hypothesized that the associations among these variables and WS might differ for women reporting BE+LOC, relative to NBE participants, such that WS would be associated with more pathological behaviors among the BE+LOC group. Second, the genetic and environmental sources of variance were estimated in each subsample. We hypothesized that genetic influences on WS would be stronger in the BE+LOC group, relative to the NBE group, based on results of prior twin studies in the area of eating disorders.