بررسی رابطه بین خویشتن داری غذایی و پرخوری: اثر متفاوت عوامل استرس زای اصلی و فرعی

This study sought to examine the complex interactive impact of major stress and minor stressors on the relation between dietary restraint and binge eating. Participants were 497 undergraduate females who completed an online questionnaire that included measures of binge eating (modified version of the bulimia scale of the Eating Disorder Inventory-2; EDI-2), major life stressors (the Social Readjustment Rating Scale; SRRS), minor stressors (Daily Stress Inventory; DSI), and dietary restraint (Restraint Scale; RS). A hierarchal linear regression revealed a significant three-way interaction among dietary restraint, life event stress, and daily stress that accounted for a significant proportion of the variance in binge eating above and beyond all main effects and two-way interactions. Findings suggested that the interactive relationship among dietary restraint and daily stress is present only under conditions of high life event stress. Overall, the relationship between dietary restraint and binge eating appears to be quite complex and dependent upon differential levels of daily and life event stressors.

Binge eating is an essential component of the diagnostic criteria for both bulimia nervosa and binge eating disorder and has been shown to be associated with other psychiatric symptomatology (e.g., depression; Crow et al., 1996 and Paxton and Diggens, 1997). Thus, understanding factors that impact binge eating will not only add to the literature on disordered eating, but may also improve our understanding of other psychological disorders as well. Extant cross-sectional and longitudinal data indicate that dietary restraint is a significant predictor of binge eating (Jacobi et al., 2004, Polivy et al., 1988, Stice and Agras, 1998 and Stice, 2001). Several hypotheses have been put forth regarding these predictive associations. For example, researchers have hypothesized that dietary restraint leads to binge eating through physiological deprivation, i.e., decreased caloric intake leads to binge eating in the body's defense of its weight set-point (Nisbett, 1972). Alternatively, because dieting is a cognitively mediated activity (i.e., making a decision not to eat even when hungry), researchers have theorized that dieters engage in binge eating when their cognitive control is temporarily disrupted (Polivy and Herman, 1985 and Ruderman, 1986). This phenomenon has been termed the “abstinence violation effect” (Marlatt & George, 1984) and is proposed to occur when small violations in cognitive restraint over eating are interpreted as failure to maintain control and thus, the individual forgoes all control and binge eats. Finally, investigators have recently argued that dietary restraint represents an “intent” to diet rather than actual caloric restriction (Stice et al., 2004 and Stice et al., 2007). These later theories posit that individuals who have a desire to diet are at increased risk for binge eating even in the absence of actual decreased caloric intake, as a general preoccupation with food and/or tendency towards overconsumption is associated with high levels of both dietary restraint and binge eating (Stice, Martinez, Presnell, & Groesz, 2006) Regardless of the exact explanatory mechanisms, dietary restraint has been established as a clear and important risk factor for the development of binge eating. Likewise, stress has been theorized to be a potent risk factor for binge eating (Crowther et al., 2001, Hansel and Wittrock, 1997 and Wolff et al., 2000). Stress is a multi-dimensional construct that has been defined in terms of daily hassles (e.g., forgetting one's keys) as well as major life events (e.g., divorce). Importantly, both forms of stress have been associated with binge eating. Individuals with bulimia nervosa and binge eating disorder have been found to experience a significantly greater number of stressful major life events prior to the onset of their eating disorder (Pike et al., 2006, Rojo et al., 2006 and Welch et al., 1997). In addition, daily stress has been associated with binge eating in clinical and sub-clinical samples of binge eating women (Crowther et al., 2001, Freeman and Gil, 2004, Smyth et al., 2007 and Wolff et al., 2000). For example, a recent ecological momentary assessment study reported higher levels of daily stress on binge days versus non-binge days and increasing levels of stress immediately prior to binge episodes in women with bulimia nervosa (Smyth et al., 2007). High levels of daily stress are also related to overeating behavior in nonclinical samples (Greeno and Wing, 1994 and Michaud et al., 1990). Interestingly, one of the most robust predictors of stress-induced overeating is the presence of high levels of dietary restraint. Both laboratory and naturalistic studies demonstrate that restrained eaters tend to increase their food intake as a result of stress, whereas unrestrained eaters are either unaffected by stress or eat less (Cools et al., 1992 and Greeno and Wing, 1994; Heatherton et al., 1991 and Wardle et al., 2000). These findings clearly suggest that stress and restraint interact to influence eating behavior. Stress–restraint interactions have also been reported in the animal literature; the combination of caloric restriction and stress increases the consumption of palatable (i.e., high fat) food in female rats as compared to either dietary restriction or stress alone (Hagan et al., 2002). These animal findings provide additional support for the presence of interactions between dietary restraint and stress that may be present in humans as well. Importantly, most studies that have examined the interactive effects of restraint and stress on binge eating in humans have been conducted in the laboratory and have focused on the isolated effect of a specific stressor (e.g., watching a stressful video, attempting unsolvable puzzles, giving a speech) on eating behavior. Given that the presence of high levels of life event and daily stress appear to be important for binge eating (e.g., Welch et al., 1997 and Wolff et al., 2000), it is necessary to examine interactive relationships using multiple measures of stress that assess both major life event as well as daily hassle stress. Understanding how these different forms of stress are related to binge eating when considered together can help us to develop and refine theories of how stress might impact binge eating. Given the above, the aim of the present study was to examine the effects of different forms of stress on the relationship between dietary restraint and binge eating. Measures of both daily stressors (e.g., minor traffic violation) and major life event stressors (e.g., change in career) were used in order to examine the differential effects of stress as moderators of dietary restraint/binge eating associations. It was hypothesized that dietary restraint/binge eating associations would be strongest in individuals with high levels of daily or major life event stress. In addition, this study sought to explore more complex, three-way interactions between dietary restraint, daily stress, and life event stress on binge eating behaviors. Many individuals experience both high levels of daily stress and life event stress, and the combination of these forms of stress with restrained eating may be especially “risky” for binge eating.