Intrasexual Competition and Other Theories of Eating Restriction 17

Norman P. Li, April R. Smith, Jose C. Yong, and Tiffany A. Brown

Over 24 million people in the United States criteria for AN, BN, or BED, are diagnosed with and as many as 70 million worldwide are an other specified feeding or eating disorder afflicted with an eating disorder, and many (OSFED). Subsumed within OSFED are atypical more are undiagnosed (Renfrew Center Founda- AN, subthreshold BN, subthreshold BED, purg- tion for Eating Disorders, 2003). Indeed, 80 % ing disorder (PD), and night eating syndrome of women report being dissatisfied with their (NES). body shape (Smolak, 1996), and half of teenage DSM-5 AN is primarily characterized by girls skip meals, vomit, or engage in other the restriction of food intake leading to signifi- extreme weight control practices (Neumark- cantly low body weight (i.e., less than minimally Sztainer, 2005). In this chapter, we describe the normal for age, sex, developmental trajectory, etiology and epidemiology of disordered eating and physical health). Additional criteria for AN and review both traditional, non-evolutionary include an intense fear of gaining weight or perspectives and evolutionary perspectives, with becoming fat or persistent behavior that interferes particular attention given to the intrasexual com- with weight gain, and body image disturbance. petition hypothesis. We then close the chapter by AN also includes two subtypes, to denote the considering unanswered questions and future presence or absence of binge eating/purging dur- directions for research on disordered eating. ing the current episode. The restricting subtype specifies presentations with weight loss occurring as a result of dieting, fasting, and/or excessive Disordered Eating exercise. The binge eating/purging subtype includes individuals who have regularly engaged Three major categories of eating disorders exist in binge eating or purging (self-induced vomiting, in the Diagnostic and Statistical Manual of Men- laxatives, diuretics) or both. AN affects dispro- tal Disorders, Fifth Edition (DSM-5; American portionately more women than men, with lifetime Psychiatric Association, 2000): anorexia nervosa prevalence rates approximating 0.9 % in women (AN), bulimia nervosa (BN), and binge eating and 0.3 % in men (Hudson, Hiripi, Pope, & disorder (BED). Individuals with a clinically sig- Kessler, 2007). nificant disorder of eating that does not meet the BN is primarily characterized by recurrent episodes of binge eating and inappropriate com- pensatory behaviors to prevent weight gain. N.P. Li (*) Binge eating episodes are typified by both Singapore Management University, School of Social eating an amount of food that is definitely larger Sciences, 90 Stamford Road, Level 4, Singapore 178903, Singapore than what most people would consume within e-mail: [email protected] a 2-h period and experiencing a sense of

V.A. Weekes-Shackelford and T.K. Shackelford (eds.), Evolutionary Perspectives on Human Sexual 323 Psychology and Behavior, Evolutionary Psychology, DOI 10.1007/978-1-4939-0314-6_17, # Springer Science+Business Media New York 2014 324 N.P. Li et al. loss of control over the eating episode. Inappro- mental, or medical disorder. Given that the priate compensatory behaviors can either include DSM-5 has just recently been published, there purging (self-induced vomiting, laxative use, is not enough information to determine the prev- or diuretics) or non-purging behaviors (fasting alence of OSFED. The lifetime prevalence esti- or excessive exercise), to influence weight or mate of DSM-IV eating disorder not otherwise shape. To meet full criteria for BN, these binge specified (EDNOS) was approximately 4.62 %, eating and compensatory behaviors must occur, which was greater than those observed for both on average, once per week for 3 months. Addi- AN and BN (Le Grange, Swanson, Crow, & tionally, BN is characterized by an undue influ- Merikangas, 2012); however, given that the ence of weight and shape on self-evaluation and changes made to DSM-5 AN, BN, and BED cannot be diagnosed concurrently with AN. As were meant to reduce the preponderance of the with AN, BN affects a greater proportion of residual EDNOS category, the estimates of females, with lifetime prevalence estimates OSFED are likely to be somewhat lower than approximating 1.5 % of women and 0.5 % of those for EDNOS. men (Hudson et al., 2007). Regarding course and outcome, AN has BED is characterized by recurrent binge typically been associated with a more chronic eating episodes in the absence of any recurrent course and poorer prognosis compared to BN compensatory behaviors. To meet criteria for and EDNOS (Keel, Brown, Holland, & Bodell, BED, three of several cognitive and behavioral 2012; Steinhausen, 2002). Indeed, AN is asso- features must also be associated with the binge ciated with lower remission rates compared to episodes, including: eating more rapidly, eating BN over the course of 10 or more years of until uncomfortably full, eating when depressed, follow-up (approximately 50 % for AN and eating in the absence of hunger, eating alone due 75 % for BN; Keel & Brown, 2010). Relapse to embarrassment over food consumption, or affects a substantial minority of individuals feeling disgusted or guilty after eating. To meet who achieve remission, with one study finding full criteria for BED, binge eating episodes must that relapse occurred in 26.0 % of patients occur on average at least once per week for three with AN compared to 17.7 % of patients with months. BED affects more females than males, BN (Castellini et al., 2011). These remission with lifetime prevalence estimates at 3.5 % and rates support the relatively more chronic course 2.0 %, respectively; however, the gender ratio is of AN. Consistent with this, the longitudinal far less skewed than in AN and BN (Hudson et stability of AN is more common than diagnostic al., 2007). As a residual category, OSFED crossover; however, approximately 18 % of includes any clinically significant disorder of individuals initially diagnosed with AN cross- eating that does not meet criteria for AN, BN, over to a diagnosis of BN at some point (Keel or BED, including subthreshold and atypical et al., 2012). Further supporting the severity of forms of AN, BN, and BED, along with alterna- the disorder, AN has been consistently associated tive symptom configurations. These alternative with increased mortality (Herzog et al., 2000; symptom configurations include PD and NES. Sullivan, 1995) and suicidality (Preti, Rocchi, PD is characterized by recurrent episodes of Sisti, Camboni, & Miotto, 2011). Indeed, risk purging (vomiting, laxative, or diuretic use) to for death by suicide among individuals with AN control weight or shape in the absence of binge was found to be approximately 28-fold that of the eating episodes among normal weight general population (Preti et al., 2011). individuals. NES is primarily characterized by Research has supported a slightly more recurrent episodes of night eating (either eating favorable prognosis for BN as compared to after awakening from sleep or by excessive food AN. BN appears to have lower remission consumption after the evening meal). NES must rates compared to bulimic-type EDNOS and be associated with clinical distress/impairment BED at shorter-term follow-up (Agras, Crow, and cannot be better explained by another eating, Mitchell, Halmi, & Bryson, 2009; Milos, Spindler, 17 Intrasexual Competition and Other Theories of Eating Restriction 325

Schnyder, & Fairburn, 2005); however, rates EDNOS compared to AN persist over longer-term between diagnoses appear more comparable at follow-up, differences between EDNOS and BN longer-term follow-up (Fichter & Quadflieg, tend to diminish over time (Keel & Brown, 2007; Grilo et al., 2007; Keel, Gravener, Joiner, 2010). Among those who do achieve remission, & Haedt, 2010). Similar to AN, BN is more relapse rates are comparatively lower to those likely to remain stable over time than to observed in AN, supporting a more favorable crossover to another eating disorder. Among outcome across EDNOS diagnoses. Indeed, those who do change diagnoses, the most Castellini and colleagues (2011) found that common crossover patterns are from BN to among EDNOS diagnoses, relapse occurred in AN (7 %) and from BN to BED (2 %; Keel 4.4 % of those with subthreshold AN, 15.6 % of et al., 2012). Notably, the crossover rate those with subthreshold BN, and 12.1 % of those from BN to AN is lower than that of AN to with subthreshold BED. Although few studies BN, supporting the greater severity of AN. have examined the stability of PD, one short- Evidence supports elevated mortality rates term study provides evidence for greater stability among individuals with BN (Franko & Keel, of diagnosis than crossover, with crossover to BN 2006; Nielsen, 2003); however, these rates have being relatively low (4 %; Keel, Haedt, & Edler, typically been lower than those observed in 2005). Studies have also provided evidence for an AN. Individuals with BN are also at increased elevated rate of death among EDNOS, somewhat risk for suicide (Crow et al., 2009; Preti et al., comparable to BN, but lower than that for AN 2011; Smith et al., 2013), with an approximately (Button, Chadalavada, & Palmer, 2010; Crow 14-fold higher risk of suicide compared to that of et al., 2009). EDNOS also appears to have the general population (Preti et al., 2011). increased risk for suicide, similar to rates BED appears to have a more favorable course observed for BN (Crow et al., 2009). and outcome compared to both AN and BN. Remission rates are generally higher for individuals with BED (up to 82 %) and individuals with BED Traditional (Non-evolutionary) appear to achieve remission in a shorter amount of Perspectives on Disordered Eating time than either those with AN or BN (Agras et al., 2009). Remission among 11.4 % of patients with Since the description of AN in 1873 by BED (Castellini et al., 2011). Unlike the diagnostic Sir William Gull, thousands of articles and stability observed across AN and BN, BED is books have been written on the possible causes actually more likely to crossover to BN than to of eating disorders (bulimia was not described remain stable (Fichter & Quadflieg, 2007;Keelet until 1979; thus, earlier perspectives on eating al., 2012). Also unlike AN and BN, there does not disorder etiology focused on AN). Early models appear to be an increased risk of death by suicide in tended to highlight specific factors, like puberty BED (Keel et al., 2012). Given the new designation or family, to be at the root of the development of of named syndromes (i.e. atypical AN, PD) and eating disorders. However, most current resear- heterogeneity within the category of OSFED, rela- chers agree that the etiology of eating disorders tively few studies have examined course and out- is complex and multiply determined, and modern come in this group, which limits definitive researchers discuss the development of dis- conclusions regarding prognosis for specific types ordered eating in the context of an integrated of OSFED. Studies examining DSM-IV EDNOS biopsychosocial model. Despite this, various have supported more encouraging outcomes as etiological perspectives differ by the relative compared to AN and BN in the short term (Keel importance they accord for the role of factors &Brown,2010). While higher remission rates for such as family, peers, culture, emotion regulation, 326 N.P. Li et al. interpersonal strategies, cognitive processes, and Psychosomatic Families biology. Below, we briefly review each of these perspectives. Around the same time as Bruch, Minuchin and colleagues (1975, 1978) developed a theory of AN that laid the etiological blame on the family, The Onset of Puberty coining the term “psychosomatic family” to describe families of girls with AN. According One of the early influential writers on AN was to Minuchin et al. (1978), these families were Hilde Bruch, who focused on puberty as a characterized by high conflict avoidance, high pivotal trigger for the development of AN. enmeshment, and great emphasis on bodily Puberty is a time when young women’s bodies functions. Minuchin stated that the child with go through a variety of changes, including AN used her illness as a way to gain control in increased fat accumulation. Further, puberty the context of an overcontrolled family. is also associated with greater challenges in According to Minuchin, “for the sick child, the terms of role expectations and peer relationships. experience of being able to protect the family by A large proportion of eating disorders onset using the symptoms may be a major reinforce- around puberty; thus, Bruch suggested that AN ment for the illness” (p. 31). However, although results in those adolescent girls who experience family therapy is a successful form of treatment puberty as overwhelming. She speculated that for adolescents with AN (e.g., Lock, 2011), the these adolescent girls desired to revert to a role of the psychosomatic family in the develop- prepubertal stage, one before the overwhelming ment of AN has not been empirically supported demands of puberty were placed on them (1978). (e.g., Eisler, 2005). Thus, although families are Similarly, writing some 20 years later, Crisp important in the treatment process, current (1997) speculated that young women were theories do not suggest that controlling families motivated to engage in self-starvation as a way “cause” eating disorders. to revert to an earlier pubertal stage. In fact, Crisp hypothesized that women with AN had such a pronounced phobic avoidance of their adult body Western Culture, Media, that they engaged in severe dietary restriction in and the Thin Ideal order to avoid developing an adult physique. Although these theories hold some intuitive More recent researchers have speculated that appeal, they are largely untested. Further, they eating disorders are a product of modern Western fail to account for various aspects of disordered culture. Support for this comes from the fact that eating. For instance, they do not address eating disorders are most common in Western the development of disordered eating in boys societies, and there appears to be some evidence and men, despite the fact that men account that the incidence of bulimia is increasing for approximately 10–25 % of individuals along with Westernization (Keel & Klump, diagnosed with an eating disorder (Carlat, 2003). More specifically, some researchers have Camargo, & Herzog, 1997; Weltzin et al., 2005). suggested that the internalization of the Western Additionally, these explanations do not take beauty ideal, which has become thinner over into account the development of eating disorders the past 60 years (Seifert, 2005), is a major in prepubertal or postpubertal women, though contributor to the development of eating dis- these two groups are noted to make up a propor- orders (e.g., Striegel-Moore, Silberstein, & Rodin, tion of eating disorder cases (e.g., Keel et al., 1986; Sypeck, Gray, & Ahrens, 2004). 2010; WCEDCA, 2007). Moreover, these accounts Thin-ideal internalization results when indivi- fail to explain the development of eating disorders duals internalize attitudes that are revered by in individuals who do not express maturity fears. sources such as peers, media, and family. It 17 Intrasexual Competition and Other Theories of Eating Restriction 327 is hypothesized that failure to live up to the thin (e.g., Birkeland, Thompson, & Herbozo, 2005; ideal creates body dissatisfaction (Thompson & Dittmar & Howard, 2004). These findings are Stice, 2001). Body dissatisfaction is a well- supported by a recent meta-analysis of experi- established risk factor for disordered eating mental and correlational studies, which found (Stice & Shaw, 2002); thus, it is believed that small to moderate effects for the impact of thin- thin-ideal internalization leads to body dissatis- ideal media exposure on body image concerns faction, which in turn leads to disordered among women (Grabe et al., 2008). eating. Other researchers have emphasized the Although current evidence suggests that role of social comparison processes (Festinger, culture may play a role in the development of 1954) in the development of body dissatisfaction. eating disorders, culture is clearly not the whole According to the appearance comparison per- story, as not everyone who is exposed to and spective, exposure to a host of idealized, thin internalizes the thin ideal develops an eating images forces individuals to make upward disorder. In addition, although there is evidence comparisons between themselves and the idealized that the incidence of bulimia has been increasing images; the result of these upward comparisons since its introduction into the DSM in 1983, is believed to be the dissatisfaction in one’s the incidence of AN does not appear to be appearance (Thompson, Heinberg, Altabe, & increasing (Keel & Klump, 2003). Further, there Tantleff-Dunn, 1999). These upward compa- are numerous accounts of AN that predate the risons are thought to be particularly pernicious rise of thin ideal in Western culture, including for individuals who internalize the thin ideal saints like Catherine of Sienna, who engaged (Thompson, van den Berg, Roehrig, Guarda, & in severe dietary restriction and sometimes fasted Heinberg, 2004). to the point of death (Keel, 2005). There is a large body of research that supports positive relationships between media consump- tion, body dissatisfaction, and disordered eating Peer Influence (cf. Grabe, Ward, & Hyde, 2008). Additionally, studies have found cross-cultural support for the Some researchers place more emphasis on the role association between Western media and prob- of peer influence over societal influence in the lematic eating behaviors. For example, Becker, development of eating disorders. Peer influence Burwell, Herzog, Hamburg, and Gilman (2002) models build off of learning theory and suggest examined eating behaviors among adolescent that peers inculcate certain behaviors (e.g., laxa- Fijian girls before and after the arrival of tive use) and beliefs (e.g., the importance of a slim Western TV. After 3 years of Western TV expo- body) in other peers (Levine, Smolak, & Hayden, sure, the authors reported self-induced vomiting 1994). In a study involving friendship groups, went from being nonexistent in the population to Paxton, Schutz, Wertheim, and Muir (1999) being endorsed by 11.3 % of the population. found that cliques were similar with respect to Further, there was a reported 16.5 % increase their body image concerns, use of compensatory in clinical levels of disordered eating attitudes behaviors, and dietary restraint. Further, these (as measured by a score of 20 or above on the authors found that a clique’s use of compensatory Eating Attitudes Tests; Becker et al., 2002). behaviors accounted for unique variance in the Experimental studies have also supported this prediction of an individual clique member’s relationship. In a typical design, participants engagement in compensatory behaviors, over are randomly assigned to view either thin and above a host of well-known contributors images or normal weight images; researchers to disordered eating, like BMI, depression, and have continuously found that participants report self-esteem. As with sociocultural models, limita- greater body dissatisfaction after being exposed tions of peer influence models include a lack of to images exhibiting the thin ideal as compared specificity. In other words, peer influence is so to the participants who do not view this ideal broad that if it was a necessary contributor to 328 N.P. Li et al. eating disorders, then we would expect much Cognitive Biases higher rates of eating disorders. Leading cognitive theories of AN and BN hold that extreme overvaluation of shape and Interpersonal Formulation weight is central to the disorders (e.g., Fairburn, Shafran, & Cooper, 1998). Disordered cognitions Building off of a peer influence model, the inter- and cognitive biases are believed to play a personal formulation model of eating disorders major role in the development and maintenance (Rieger et al., 2010) proposes that in response to of eating disorders (e.g., Cooper, 1997, 2005; negatively valenced social interactions, indivi- Shafran, Lee, Cooper, Palmer, & Fairburn, duals may engage in disordered eating in an 2007). Specifically, cognitive theories posit attempt to repair self-esteem and regain their that people with eating disorders hold dysfunc- sense of self. Supporting evidence for this tional beliefs about their eating habits, shape, and model comes from multiple studies which have weight. These core beliefs perpetuate negative found that difficult interpersonal situations trigger automatic thoughts and attentional biases in binge-like behavior (e.g., Baumeister, DeWall, the processing of information (e.g., attending Ciarocco, & Twenge, 2005; Tanofsky-Kraff, only to information regarding one’s body size). Wilfley, & Spurrell, 2000). For instance, study Thus, behaviors that reduce these negative participants who were told that they had been thoughts, such as restricting food intake, are rejected by their peers ate a significantly larger highly reinforcing and contribute to the chroni- amount of cookies as compared to non-rejected city of the disorder. participants (Baumeister et al., 2005). Recent work by Guardia and his colleagues The interpersonal formulation model (Rieger (2012) suggests that individuals with eating et al., 2010) further stipulates maintenance factors. disorders not only think they are bigger than Engagement in disordered eating behaviors is they actually are, but they perceive themselves believed to increase interpersonal problems; in that way as well. In their study, individuals with turn, these interpersonal problems exacerbate AN exhibited marked distortions regarding the eating disorder symptoms. Support for the size of their bodies as compared to controls. escalation of disordered eating in response Specifically, when asked to indicate whether to interpersonal difficulties comes from a longi- or not they would be able to pass through a tudinal study which examined the effect of door opening that was definitely large enough negative feedback seeking on eating disorder- for them to pass through, the participants with related variables (Joiner, 1999). Over the course AN were more likely to indicate that they could of 5 weeks, this study found that among college- not as compared to the controls. Further, this aged women, interest in negative feedback led perceptual disturbance was found to be specific to body dissatisfaction and, in turn, increased to their own bodies; individuals with AN could bulimic symptoms. Additionally, Rieger and correctly judge whether someone else could or colleagues (2010) hypothesize that indirect could not fit through a door opening. sources of evaluative information, such as social Experiments that have used implicit tasks have comparisons, lead to increased body dissatisfac- found support for attentional biases to shape- and tion and disordered eating. In support of this weight-related cues among individuals with disor- claim, an experimental study found that female dered eating. For example, Ferraro, Andres, participants exposed to a thin confederate Stromberg, and Kristjanson (2003) found that reported worse body dissatisfaction as compared individuals who were at risk for developing to female participants exposed to a normal an eating disorder were faster at responding to weight confederate (Krones, Stice, Batres, & fat-related words (e.g., heavy, plump, cellulite) Orjada, 2005). than words unrelated to fat, whereas control 17 Intrasexual Competition and Other Theories of Eating Restriction 329 subjects were faster at recognizing “nonfat” aversive self-awareness. Due to methodological words than “fat” words. Additionally, Ahern, considerations, it has been difficult to design Bennett, and Hetherington (2008) found that studies that can measure affective states during participants who had positive implicit attitudes a binge episode, thus making it difficult to toward images of underweight women had higher garner concrete support for the escape model drive-for-thinness scores on the Eating Disorder of binge eating. However, with the development Inventory-2 and chose lower ideal body sizes of psychophysiological ambulatory monitoring, than did participants who had more positive which allows for the measurement of psycho- implicit attitudes toward normal weight models. physiological correlates of emotion, such as heart rate variability, respiratory sinus arrhyth- mia, and skin conductance (Blascovich, Mendes, Emotion Regulation Vanman, & Dickerson, 2011), it may be possible for future studies to use these types of methods Although cognitive processes figure prominently to more accurately assess affective responses in many models of eating disorder development, during a binge episode. emotion regulation is considered by some to be particularly important in the development of eating disorders that involve binge eating Biology (i.e., BN, BED). The affect regulation model makes two primary predictions about the rela- With the advent of other new technologies tionship between emotion and binge eating: like the functional magnetic resonance imaging (1) increases in negative affect trigger binge (fMRI) and methodologies like genome-wide eating and (2) binge eating has a palliative association studies (GWAS), biological perspec- effect and thus reduces negative affect (Hawkins tives on the etiology of eating disorders have & Clement, 1984). In their meta-analysis of come to prominence. Beginning in the 1980s, 36 studies using ecological momentary assess- family and twin studies have repeatedly shown ment (EMA) methodologies, Haedt-Matt and evidence of familial aggregation of eating Keel (2011) examined the validity of both disorders (Bulik et al., 2006; Strober, Freeman, of the hypotheses of the affect regulation Lampert, Diamond, & Kaye, 2000). Using model. Their findings indicated that negative findings from twin studies, researchers have affect preceded binge eating; however, the meta- estimated the heritability of AN to be 33–84 % analysis also found that negative affect increased and bulimia to be 28–83 % (Zerwas & Bulik, following a binge, in opposition to the second 2011). Thus far there has been only one hypothesis of the affect regulation model. twin adoption study that has been published (Klump,Suisman,Burt,McGue,&Iacono,2009). Participants for this study were 123 adopted Escape and 56 biological female siblings. This study found that the majority of variance (59–82 %) The escape model of binge eating (Heatherton & in eating disorder symptoms was accounted Baumeister, 1991) is related to the affect for by genetic factors, while the remainder regulation model in that it gives affect a was accounted for by non-shared environmental primary role; however, it holds that individuals factors. Interestingly, shared environmental factors, engage in binge eating as a way to escape from which include the family environment, did not negative emotional states (as opposed to an account for a significant proportion of the attempt at decreasing negative emotional states). variance. This theory suggests that in the face of negative Two primary approaches have been used in affect, individuals turn to binge eating as a order to uncover potential candidate genes that way to narrow cognitive processes and reduce may play a role in the development of eating 330 N.P. Li et al. disorders: association studies and GWAS. Thus These findings mesh with the observations far, findings from various association studies of earlier writers, such as Bruch and Crisp, suggest that likely gene candidates are those who suggested that puberty is a trigger for that are involved in the serotonergic and dopa- eating disorders; however, these findings suggest minergic systems and in weight regulation a more central role for biological factors that (Hebebrand & Remschmidt, 1995). Currently, onset at puberty as opposed to environmental only one GWAS study has been published; factors, though likely both are important. this study included over a thousand individuals Further, there appear to be important neuro- with AN and close to 4000 control subjects biological weaknesses in individuals with eating (Wang et al., 2010). The authors reported several disorders. For instance, individuals with AN have suggestive single nucleotide polymorphisms been noted to have altered reward processing, (SNPs), which are involved in the transmission poor set-shifting, and loose central coherence and regulation of neurotransmitters; however, (e.g., Lopez, Tchanturia, Stahl, & Treasure, none were significant at the genome-wide thresh- 2009; Roberts, Tchanturia, & Treasure, 2010). old. The lack of significant findings is likely due In a recent study by Danner et al. (2012), three to the small sample size for this type of study. groups of participants (women with current AN, Generally speaking, studies are only able to recovered women, and healthy control women) detect SNPs with at least five times as many completed a battery of neuropsychological ill participants as in the Wang et al. (2010) instruments (e.g., Berg’s Card Sorting Task, study (Kim, Zerwas, Trace, & Sullivan, 2011). Rey-Osterrieth Complex Figure Test, Iowa Thus, the results of these types of studies are Gambling Task). This study found that both ill promising, but very preliminary, and ultimately, and recovered women with AN demonstrated the field needs more studies with greater power set-shifting problems; further, individuals with in order to detect effects. Fortunately, a GWAS impaired set-shifting also displayed central with a target sample size of 3000 subjects with coherence weaknesses. These findings suggest AN is underway (Bulik, Collier, & Sullivan, that a rigid and inflexible thinking style may 2011). be associated with the development and main- Recent work also suggests that hormones tenance of AN. However, currently there is likely play an important role in the develop- not strong evidence that these weaknesses ment of eating disorders (e.g., Klump et al., play a role in the development of eating dis- 2012; Quinton, Smith, & Joiner, 2011; Smith, orders due to a lack of prospective studies Hawkeswood, & Joiner, 2010). Specifically, examining potential neuropsychological impair- several studies have found that prenatal testos- ments in eating disorders. Thus, it is unclear terone levels were higher among controls as if these impairments predate the onset of the compared to women with bulimic symptoms, disorder or are a consequence of the disorder. and thus, prenatal testosterone may protect The above summary of leading etiological against bulimic disorders through its organiza- perspectives is far from exhaustive; due to tional effects on the brain (Culbert, Breedlove, space limitations, we did not discuss more Burt, & Klump, 2008; Klump et al., 2006; Smith general factors, such as depression and low et al., 2010). Further, Klump and colleagues self-esteem, or highly intrapersonal factors, like (2012) have posited that ovarian hormones personality or the experience of traumatic events, released at puberty play a role in the develop- like sexual abuse, though all of these other ment of disordered eating and help explain both factors have been found to be associated with the sex difference in eating disorders and the disordered eating. timing of onset, which is often during puberty. All in all, there is a multitude of psychological Specifically, they speculate that puberty and perspectives through which eating disorders have the attendant effects of ovarian hormones may been examined. Together, the extensive research activate genetic risk in girls (Klump et al., 2012). suggests that many proximate causes may be 17 Intrasexual Competition and Other Theories of Eating Restriction 331 involved in the onset and maintenance of dis- In addition to these functions, fat has also been ordered eating. In addition, biological research, implicated for female mammals in the onset and including the results of various behavioral maintenance of ovulation (Frisch, 1990), work- genetics studies, indicates a significant genetic ing through the organism’s endocrine function component. Looking for broader, more ultimate (Fishman et al., 1975; Frisch et al., 1981; Nimrod explanations, some theorists have proposed how & Ryan, 1975). Furthermore, fat is important as a eating restriction and disordered eating might source of calories for the success of pregnancy reflect underlying psychological mechanisms that and lactation (Brown & Konner, 1987). Sex have evolved to provide adaptive benefits. We now differences in the distribution and abundance of examine each of these evolutionary perspectives. adipose tissue in humans (e.g., Enzi et al., 1986) additionally indicate that natural selection has played a critical role in shaping the anatomy Evolutionary Perspectives and development of fat, lending further credence on Disordered Eating to the view that fat serves important survival and reproductive functions. Thus, if attitudes Evolutionary psychology provides ultimate expla- toward fatness in women, perceived either in nations for various human thoughts, feelings, others or oneself, have any evolutionary impor- and behaviors (Buss, 1995). Although starving tance, that importance ultimately depends on oneself can be quite detrimental to one’s health some biological function of adipose tissue. Evolu- or even fatal, there are reasons to believe that tionary hypotheses about standards of physical adaptive mechanisms may underlie eating restric- appearance and beauty are hence, at some level, tion and the prevalence of disordered eating. attempts to explain how observed patterns in In this part, we consider various evolutionary attitudes toward female fatness and in eating hypotheses that propose how negative eating behavior could have, at least in ancestral attitudes and practices may represent adaptations. conditions, improved the fitness of individuals relative to other possible patterns.

Biological Functions of Fat Reproductive Suppression Hypothesis In order to understand how an evolutionary per- spective can account for eating disorders in One of the most prominent evolutionary theories women, consideration should be given to the for eating disorders is the reproductive suppres- biological functions of adipose tissue (i.e., fat) sion hypothesis (Condit, 1990; Salmon, Crawford, in mammals and, more specifically, mammalian Dane, & Zuberbier, 2008;Surbey,1987;Voland females. Adipose tissue has been viewed as hav- &Voland,1989). This hypothesis suggests that ing two main survival functions for mammals. natural selection may have shaped a mechanism First, it primarily serves as storage for calories in women that alters their proportion of body fat through a reserve of lipids, which are meta- in order to adjust their reproduction in accord bolized to meet the energy needs of the with socioecological conditions. This hypothesis body (Cahill, 1982; Norgan, 1997; Pond, 1978). was borne out of two well-known biological Second, adipose tissue may have evolved as an concepts that were derived from the observation adaptation for thermal insulation, accumulating that fat affects the onset and maintenance of in subcutaneous tissue and providing protection ovulation. from heat and cold (Gesta, Tseng, & Kahn, The first concept, adaptive reproductive sup- 2007), although this latter point has been pression, argues that as reproduction is a highly more controversial (cf. Pond, 1998). (For a risky and energetically demanding endeavor for more thorough review of the biological functions female mammals (Williams, 1966), a female of human adipose tissue, see Wells, 2012.) may increase her lifetime reproductive success 332 N.P. Li et al. by timing her reproductive attempts to occur explain the function of distorted body image; during desirable conditions and, correspondingly, why some more direct and less costly means to curtailing her reproductive activity at other less stop menstruation did not evolve; why women in favorable times. Natural selection may therefore modern urban cultures, who are economically select for individuals who undergo reproductive well off and have easy access to food, would suppression under suboptimal reproductive face poor reproductive prospects; and why conditions (Wasser & Barash, 1983). men are afflicted. Importantly, as noted earlier, The second concept, known as the critical amenorrhea is no longer considered to be fat hypothesis (Frisch, 1985, 1990), points out a useful indictor of AN and has been deleted that there is a positive relationship between as a criterion for AN in DSM-5 (American body fat and the likelihood of ovulation and Psychiatric Association, 2000). menstruation. On average, adipose tissue must make up at least 22 % of a woman’s body weight to maintain ovulation. Because a female’s body Model of Parental Manipulation fat contains considerable quantities of estrogen and converts androgens to estrogen, changes Voland and Voland’s (1989) model of parental in the rate of weight gain among adolescent manipulation provides an interesting account girls or in the weight of lean adult women for why eating disorders tend to occur more can influence whether ovulation occurs (Rippon, among wealthier, higher class individuals. This Nash, Myburgh, & Noakes, 1988). Indeed, for model draws on kin selection theory (Hamilton, female athletes who are bordering on this 1964) and asserts that AN may be adaptive inso- threshold, menstruation can be activated or far as it increases the helping behavior of an deactivated by the gain or loss of only a few individual with AN toward her own kin and pounds (Frisch et al., 1981). As such, in response aids their survival and reproduction while to cues relating to reproductive conditions, weight suppressing her own reproductive activity. Such control could have been an effective mechanism a kin selection-based “helper at for ancestral females to adjust reproductive effort the nest” mechanism would have been parti- (Becker, Breedlove, & Crews, 1993; Frisch, cularly beneficial in large family units, which 1990). Such socioecological cues might include were prevalent in human history until recently. stressful sexual attention from undesirable males The parental manipulation model suggests that and elevated levels of social competition between anorexia is instigated by parental dominance— females. influential parents who are highly involved in In modern urban cultures, socioecological the control of resources, offspring livelihood, cues, which would have signaled the need for and family outcomes. Particularly for wealthy temporary postponement of reproduction in ances- large families, males may have relatively better tral environments, may now be experienced at reproductive potential than females, as an abun- unprecedented levels of intensity and duration. dance of resources contributes to male mate For some women, the heightened and prolonged value more than female mate value (Trivers, body image fears and anti-fat attitudes that 1972; Trivers & Willard, 1973). Thus, if affluent abound in today’s society may result in repro- parents favor and bestow their resources onto ductive suppression mechanisms being engaged sons and spur the restriction of reproduction of continuously from preadolescence to adulthood one or a few daughters (via induced anorexia), and, thus, in the onset and maintenance of dis- better inclusive fitness outcomes may be achieved, ordered eating attitudes and behaviors during as those daughters can divert resources that that time (Salmon et al., 2008). would otherwise have gone to their own Although quite plausible, the reproductive offspring toward a male kin. suppression hypothesis nevertheless has some Consistent with this model, correlational limitations. For instance, it does not directly studies have shown that anorexic individuals 17 Intrasexual Competition and Other Theories of Eating Restriction 333 tend to worry constantly about the well-being of laboratory, a number of mammal species ignore their families, and members of anorexic families their food and exercise excessively (Epling & possess mutually overprotective attitudes (Minuchin Pierce, 1992). Lastly, when individuals starve, et al., 1975). Specifically, the likelihood of AN neurochemical signals of hunger normally are development is significantly correlated with raised, and signals for satiety and activity are having dominant and overprotective mothers typically lowered. In anorexics, however, neuro- (Steiger, Bruce, & Israe¨l, 2003) as well as overly modulators and hormones regulating appetite controlling parents (Bruch, 1988). When a and activity have been found to go against daughter is overprotected and dominated by her this usual trend and appear instead to facilitate mother, her ability to find a mate may be reduced, movement and activity (e.g., Leibowitz, 1992; further decreasing her likelihood of producing Prentice et al., 1992). Taken together, these offspring while increasing the relative benefits findings are consistent with the possibility that of helping her male kin. The parental mani- there are adaptations to deactivate desires for pulation model, however, does not account for eating and activate traveling and suggest that desires for thinness or anorexic behaviors that AN as an adaptive mechanism might have derive from sources external to the family. benefited our ancestors who were faced with food shortages to overcome the pain of hunger and energize them to migrate to more food- Adapted-to-Flee-Famine Hypothesis abundant locations. Although the evidence is encouraging, the The curious case of anorexic symptoms leading adapted-to-flee-famine hypothesis does have its to a decline in individual fitness by decreasing own set of limitations. It does not address why the carrier’s fertility and increasing the risk of individuals with AN resist eating food when death by starvation, while at the same time food is readily available and why AN is more increasing the carrier’s hyperactivity levels, led prevalent in women than men. Furthermore, Guisinger (2003) to propose that anorexia some studies have shown that not all individuals nervosa could exist in its modern form because with AN are hyperactive throughout the entire humans are adapted to flee famine. Like other phase of anorexia. primates and most mammals, humans cannot store many extra calories as fat; yet, they consis- tently faced periodic waves of famine. As Restricted Eating as Response to Threat such, in nomadic tribes, anorexia nervosa might have been a way to help humans overcome Gatward (2007) proposed that response to threat food shortages during periods of famine or while may be a reason why individuals get trapped traversing vast distances, by facilitating the in an anorexic cycle. Because humans are social migration from depleted environments to greener animals whose survival depends on group inclu- pastures. sion, there will inevitably be competition for Findings from nonhuman populations provide status within the group (Baumeister & Leary, preliminary evidence supporting this view. Food- 1995). Within-group competition leads to the restricted rats with access to a running wheel threat of being expelled from the safety of one’s and lean-bred pigs with wasting pig syndrome social group, which, in the ancestral past fraught have been found to reject food (Epling & Pierce, with myriad dangers, would have likely meant 1988; Treasure & Owen, 1997). More generally, certain death. Demonstrating status is thus of Mrosovsky and Sherry (1980) documented the paramount importance, as status is an indicator cessation of eating and weight loss of a number of one’s worth to remain in the group. Until of nonhuman species during their seasonal recently, fatness was a sign of good resources, migrations. Animals also increase activity in as only the wealthy could afford to be over- times of food shortage. When starved in the weight. In many cultures today food is relatively 334 N.P. Li et al. abundant and cheap, and resistance to food has While such a perspective has tended to become a modern sign of status and self-control reside within the grounds of proximate, social, (Stevens & Price, 2000). Eating restriction could and non-evolutionary factors, Park, Schaller, and thus have emerged in order to signal high status Crandall (2007) explored the possibility that as a response to the threat of social exclusion. humans have evolved to view obesity as a Gatward borrows from the adapted-to-flee- heuristic cue connoting pathogen transmission. famine hypothesis and the adaptive suppression As signal detection of pathogens is often imper- hypothesis to explain the onset and maintenance fect, humans may have evolved to associate of AN. Perceived threat of exclusion may acti- a wide range of superficial cues, such as vate dietary restriction, which in turn may facial birthmarks and physical disabilities, with trigger the adaptive response of decreased pathogens. Humans’ behavioral immune system, appetite and increased hyperactivity to a newly in the form of aversion, can be triggered by the perceived threat of famine (caused by the perception of substantial morphological deviations; dietary restriction), and thus cause the individual thus, perceived obesity may trigger a behavioral to experience the symptoms of AN. As these immune system of aversion because gross multiple threats of social exclusion and famine, obesity represents one such deviation from real or imagined, suggest undesirable socio- species-typical morphological norms. Relatedly, ecological conditions, females are also likely overweight people are commonly stereotyped as to undergo suppressed reproductive behavior. unattractive, unclean, and unhealthy, and images Because severe weight loss removes people of overweight people arouse visceral emotions from competition for status, subsequent weight such as disgust (Harvey, Troop, Treasure, & gain could also be felt as threatening because it Murphy, 2002). Antipathy toward overweight could signify reentering within-group competition people could thus be more fundamentally the and risking attack by others and further exclu- result of a pathogen-avoidance mechanism. sion. These multiple perceived sources of threat Pathogen-avoidance mechanisms typically thus maintain restricted eating behaviors in involve hypervigilance and risk aversion, and individuals, particularly females. A limitation of avoidant responses to individuals marked by this model is that it is difficult to evaluate; disease-connoting cues are particularly strong furthermore, it does not effectively rule out alter- when perceivers feel especially vulnerable to native hypotheses. disease transmission (Schaller, Park, & Faulkner, 2003). These features allow for an adaptive rejection of individuals afflicted with actual Perceived Vulnerability to Disease contagious diseases. and Anti-fat Attitudes Consistent with their hypotheses, the authors found that perceived vulnerability to disease Another perspective argues that eating disorders significantly predicted antipathy toward over- arise out of the association between fat and weight people independently from other variables, character undesirability. Specifically, when being such as self-determination ideologies (Schaller fat implies negative traits such as laziness, irre- et al., 2003). In addition, participants who were sponsibility, lack of self-control, and other quali- primed with images depicting contagious diseases ties pertaining to character and lifestyle flaws and disease-causing agents were more likely to (e.g., Bjo¨rvell, Edman, Ro¨ssner, & Schalling, associate overweight people (as opposed to thin 1985; Fassino et al., 2002), anti-fat attitudes people) with disease using the implicit association emerge which in turn may result in restricted test compared to when they were exposed to eating in order to avoid gaining weight and, either accident primes (which eliminate the as a consequence, being associated with those possibility of negatively valenced primes as a aversive, negative traits. factor), or primes pertaining to work ethics (which 17 Intrasexual Competition and Other Theories of Eating Restriction 335 eliminate the likelihood that self-determination fertility, men’s fertility declines significantly attitudes accounted for the pattern of results). slower over the lifespan; thus, there may The perceived vulnerability to disease and have been less selective pressure for women anti-fat attitudes model focuses on antipathy to strongly prefer similar cues in their mates. toward overweight individuals other than oneself. However, because ancestral men varied in their Nevertheless, evolved disease- and pathogen- ability to provide key resources essential for avoidance mechanisms may play a role in offspring survival and eventual reproduction shaping attitudes toward one’s own weight status (e.g., Geary, 2009), women may have evolved and, thus, in the development of restricted eating. to prefer men with status and resources (Symons, This may be especially true for individuals who 1979). perceive a lack of social standing in their groups. Indeed, numerous studies have found that men In the next part, we consider an additional value physical attractiveness in their mates more evolutionary explanation that is perhaps most than women do, and women value status and consistent with all the other theories and is also resources more than men do (e.g., Buss, 1989; guided by a fundamental evolutionary theory: Li, Bailey, Kenrick, & Linsenmeier, 2002; Li, intrasexual selection (Darwin, 1871). Valentine, & Patel, 2011; Shackelford, Schmitt, & Buss, 2005). These sex-specific preferences appear to be ingrained in people’s self-concepts: Intrasexual Selection Hypothesis when considering themselves as potential long- term mates, men prioritize having status and Intrasexual selection involves members of one resources, whereas women prioritize having sex competing among themselves, usually for physical attractiveness (Li, 2007). In line with access to mates or resources. Heritable behaviors these differences, women, more than men, or features that provide an advantage in this express greater usage of intrasexual competition competition tend to be selected and passed tactics related to physical appearance, including down over the generations. Intrasexual selection dieting to improve one’s figure. Such tactics is traditionally associated with male–male com- are also judged to be more effective for female petition, as in massive male elephant seals versus male intrasexual competition (Buss, 1988). battling viciously for a large territory on a Furthermore, men are more distressed when a beach before female seals arrive for the mating rival surpasses them on financial prospects, job season (e.g., Gould & Gould, 1989). However, prospects, and physical strength, whereas women recent evidence suggests that females of many are more distressed when a rival surpasses species also engage in various forms of intense them on facial and bodily attractiveness (Buss, intrasexual competition (e.g., Clutton-Brock, Shackelford, Choe, Buunk, & Dijkstra, 2000). 2007; Rosvall, 2011). The intrasexual competition model. Drawing In humans, intrasexual competition tactics on principles of sexual selection, Abed (1998) employed by one sex tend to reflect the proposed an intrasexual competition hypothesis mate preferences of the other sex (Buss, 1988; for disordered eating, laying out the following Walters & Crawford, 1994). For instance, women’s logic. In the ancestral past, the hourglass shape fertility tends to peak at a relatively early age [i.e., waist-to-hip ratio (WHR), Singh, 1993] and decreases rapidly after 30. Thus, when was a reliable indicator of a female reproductive considering potential mates, men may have condition and capacity. As such, men evolved evolved to especially value appearance-related to strongly prefer females with low WHRs cues that indicate sexual maturity and youth. as mates because such females had high repro- Such preferences allowed ancestral men to choose ductive capacity and were also not currently mates with greater fertility and reproductive value pregnant or lactating. As women age, they not and, thus, to outreproduce men who did not only lose the hourglass shape but also tend to have such preferences. In contrast to women’s gain body mass. This is especially the case 336 N.P. Li et al. when women’s bodies are subjected to cycles in particular, urban environments—is curtailed of pregnancy, childbirth, and nursing, as they and delayed, and the birth spacing interval would have been from a relatively early age is greater, thereby allowing women to retain in the ancestral past. Thus, in addition to the a nubile shape for much longer than would be hourglass shape, bodily thinness may also have the case in an ancestral or traditional society. been reliably associated with nubility—a state Moreover, the population density in modern of fertility with no reproductive history. Whereas environments can reach several millions per WHRs are largely influenced by estrogen levels city—an extremely large-scale increase over (Cashdan, 2008; Singh, 1993), thinness may the lightly populated ancestral village where not only be influenced by hormones but may 150 might be a maximum total population also be controllable through dieting. As such, (Dunbar, 1992). Thus, in modern environments, women may have evolved to be sensitive to women are exposed to an unnaturally high num- perceptions of premature obesity and to strive ber of potential competitors who may appear for being as thin as or thinner than other young nubile and trigger intrasexual competition on nulipara. Such an adaptation may have given thinness (Salmon et al., 2008). ancestral women a competitive edge in attracting Furthermore, in modern environments, the long-term mates. person’s perceived intrasexual competitors are In modern, industrial environments, however, not limited to actual competitors. Various lines several factors may lead to a destabilization of research have demonstrated that people (their of long-term relationships and, consequently, evolved mechanisms) cannot distinguish between to a “runaway” intrasexual competition process real individuals encountered in the flesh and in which an eating restriction strategy is those seen on television, magazines, Internet, triggered and maintained to the point of ill and other forms of media (e.g., Kanazawa, health or fatality. With the formation of modern, 2002). For example, many people evaluate their industrial societies, the size and unity of extended social lives more positively after having watched families—which tended to be patrilocally organized television (Kanazawa, 2002). After being (centered around men’s genetic relatives) in the exposed to pictures of physically attractive ancestral past (e.g., Wrangham, 1999)—greatly women, women evaluate themselves more nega- decreased. Accordingly, the role of kin as well tively as potential mates and men express as the power of men in influencing mating reduced commitment to their long-term romantic markets and women’s sexual behavior greatly partners (Kenrick, Neuberg, Zierk, & Krones, diminished, leaving women to promote them- 1994). The multibillion dollar pornography selves in the mating markets and with greater industry attests to the ability of psychological autonomy in selecting mates. According to Abed mechanisms to be triggered by two-dimensional (1998), such forces likely decreased men’s pater- images (Kenrick, Gutierres, & Goldberg, 1989). nity confidence and, thus, their paternal invest- These days, people consume electronic media ment, which in turn led to a destabilization of and can expose themselves to more individuals marriage and, at the same time, an increase in 1 day than our ancestors encountered in a among women in pursuing short-term relation- lifetime. The effects of such exposure are now ships. Thus, in modern societies, there are more coming into light. For instance, a recent study individuals available for a longer time on the indicated that many healthy men in their 20s who mating market and more women competing regularly consume Internet pornography cannot with each other for mates for many more years maintain erections with their actual partners, than in the ancestral past. who likely compare unfavorably to images of Additionally, children in modern societies are naked women on the Internet (Italian men suffer no longer needed to tend to family farms or ‘sexual anorexia’ after Internet porn use, 2011). trades and instead, represent net economic losses. All in all, individuals, including women, Accordingly, reproduction in modern societies— face an inordinate number of real and virtual 17 Intrasexual Competition and Other Theories of Eating Restriction 337 same-sex competitors in the modern world. Stice, 2001) that is thought to be a product of One result of all this competition is that for Western culture may represent women’s mental some women, intrasexual competition mecha- composites (Symons, 1979) of the youngest and nisms via dietary control may be excessively most fertile-looking potential competitors for triggered, thereby leading to unhealthy dieting mates. Although adaptive for setting comparison practices and, in some instances, disordered standards in a small village setting, this compos- eating. We note here that although in this part ite in the modern world includes an unnaturally we refer to disordered eating in general, Abed high number of thin, nubile-looking competitors, (1998) makes a distinction between the two main both real and virtual, thereby leading to perpetual forms. That is, AN is viewed as a manifestation shortcomings between one’s self-evaluation and of intrasexual competition with a relatively early one’s ideal, desired state. As described above, onset in which standards for thinness are such gaps are associated with body dissatis- set extremely low, whereas BN involves a reacti- faction and attempts to eliminate the gaps via vation of intrasexual competition mechanisms various forms of unhealthy caloric restriction for thinness with a somewhat later onset. and weight reduction practices. Compatibility with other perspectives and Similarly, the intrasexual competition perspec- research. The intrasexual competition model is tive also offers insights into the numerous studies compatible with many of the findings on dis- showing links between women’s exposure to thin ordered eating reviewed earlier. For instance, images and body dissatisfaction, unhealthy eating various researchers have noted of the high attitudes, and various eating disorders. That is, incidence of eating disorders in adolescent the ultimate reason why people—in particular, females (e.g., Bruch, 1978; Crisp, 1997). Indeed, young women—are susceptible to comparisons although both young girls and older women can of thinness in the first place is because of psycho- evidence disordered eating, the average age of logical mechanisms that evolved to promote onset for anorexia nervosa is 17, and rates tend successful intrasexual competition for mates. to drop off after 25 (Substance Abuse and Such mechanisms may also be responsible for Mental Health Services Administration, 2003). various cognitive distortions and biases relating As mentioned earlier, Bruch (1978) suggested to one’s own size and shape (e.g., Cooper, 1997), that AN might be especially likely to occur in which, alongside body dissatisfaction, serve to female adolescents who experience puberty as motivate eating restriction and weight loss. overwhelming. From an intrasexual competition From an intrasexual competition perspective, perspective, puberty may be particularly over- women’s interest in consuming fashion-based whelming and a time when eating disorders media and the featured thin models may be are likely to occur because this is precisely stemming from innate, adaptive mechanisms to when competition for mates has not only set socially compare and learn from same-sex indi- in but is especially intense. Similarly, attempts viduals of higher mate value. Along these lines, to repair self-esteem as proposed by the inter- one study examined the eye movements of personal formulation model (Rieger et al., 2010) women presented with various target faces. may center around efforts to regain mate value Women with relatively high bulimotypic symp- or social status, which, for women, tends tomatology tended to fixate on physically attrac- to revolve around physical attractiveness and tive female faces versus average female faces youth. Consistent with this line of reasoning, or male faces (Maner et al., 2006). one study found that women with anorexia Empirical investigations of the intrasexual were less likely to be married than aged-matched competition model. Various studies have provided controls (45 % vs. 16 %; Sullivan, Bulik, Fear, & direct support for the intrasexual competition Pickering, 1998). hypothesis. For instance, a correlational study From the intrasexual competition perspective, found, through structural equation modeling, that the prevalent thin ideal (e.g., Thompson & female intrasexual competitiveness for mates 338 N.P. Li et al. was the underlying factor behind competition In the first study, people saw these profiles for status, perfectionism, body dissatisfaction, and then completed the Eating Attitudes Test drive for thinness, and both BN and AN (Faer, (Garner & Garfinkel, 1979), which measures Hendriks, Abed, & Figueredo, 2005). thoughts and feelings related to disordered Another study examined the relationships eating, including restriction (e.g., “I avoid eating between life history strategy, intrasexual compe- when hungry”), purging (e.g., “I have the tition, and eating disorders (Abed et al., 2012). impulse to vomit after meals”), and a strong Life history strategy was developed by evolu- desire for thinness (e.g., “I am preoccupied tionary biologists to explain how organisms with a desire to be thinner”). Women who (including humans) adaptively allocate energy, were exposed to the competitive target profiles time, and resources across their lifetime toward indicated having significantly more negative different activities (e.g., Charnov, 1993; Daan & eating attitudes (some were at clinical levels) Tinbergen, 1997). Whereas a slow life history than women exposed to the noncompetitive strategy is associated with greater somatic effort profiles. No effects were found for men, who (development of body, mind, skills, etc.) and tended to have low negative eating attitudes parental investment, a fast life history strategy in both conditions. Thus, this study indicated is associated with greater mating and reproduc- that even in the absence of attractiveness tive effort. A structural equation model indicated and thinness-related cues, instrasexual status that intrasexual competitiveness was related competition motives are capable of triggering to disordered eating behaviors; moreover, a negative/restrictive eating attitudes. slow life history strategy had negative effects A unique strength of the intrasexual compe- on disordered eating behavior both directly tition hypothesis is that it addresses eating and through its negative effect on intrasexual disorders in men. Although eating disorders pre- competitiveness. A subsequent study found dominantly occur in women, they do affect some evidence that the protective effects of a slow men, and they are disproportionately represented life history strategy may be due to its associa- in gay men (e.g., Herzog, Norman, Gordon, & tion with greater behavioral regulation, which Pepose, 1984) but not lesbian women (Striegel- is negatively associated with intrasexual compe- Moore, Tucker, & Hsu, 1990). To examine this titiveness and disordered eating behaviors (Salmon, phenomenon, in their second study, Li et al. Figueredo, & Woodburn, 2009). (2010) also investigated the effects of sexual Strong evidence for the intrasexual competi- orientation in their second study. Similar to tion model also comes from two recent investi- heterosexual men, gay men also place great gations using an experimental paradigm. First, value on youth and physical attractiveness in Li, Smith, Griskevicius, Cason, and Bryan (2010) their mates (Bailey, Gaulin, Agyei, & Gladue, conducted two studies in which participants 1994; Kenrick, Keefe, Bryan, Barr, & Brown, were exposed to a series of ten personal profiles 1995). Thus, like heterosexual women, gay men allegedly written by same-sex target individuals, compete intrasexually on appearance and may describing their interests, school and community develop similar issues of body image and eating activities, and job. The profiles conveyed either restriction due to such competition. Indeed, het- a competitive and status-seeking orientation erosexual women, but not heterosexual men, (e.g., playing to win, taking leadership positions, responded to the competitive target profiles aiming for success) or a noncompetitive and by reporting more negative eating attitudes and non-status-seeking orientation (e.g., playing for worse body image. On the other hand, gay men, fun, joining but not leading organizations, and but not lesbian women, reported more negative being content to get by). Each profile was accom- attitudes and worse body image after viewing the panied by a facial photograph of an individual competitive profiles. This specific pattern of of average physical attractiveness and normal results reflected the differing values that indivi- weight. duals’ mates place on physical attractiveness 17 Intrasexual Competition and Other Theories of Eating Restriction 339 according to their sex and sexual orientation and intrasexual competition and body dissatisfaction lent further support to the intrasexual competi- and disordered eating attitudes. Furthermore, tion model. because intrasexual competition is a key evolu- If intrasexual competition underlies the prev- tionary process for both sexes, the intrasexual alence of eating disorders in modern societies, competition model addresses why eating dis- then competitive individuals who are especially orders occur in some men. Finally, the model oriented toward the attainment of social status is consistent with separate lines of research would be expected to be particularly at risk. indicating that various modern-day ills may be To investigate this possibility, Smith, Li, and due to a mismatch between current living condi- Joiner (2011) measured women’s status aspira- tions and the ancestral environment in which tion with the status aspiration subscale of human psychological mechanisms evolved to the Achievement Motivation Scale (Cassidy & function (e.g., Buss, 2000; Kennair, 2002;Nesse Lynn, 1989; e.g., “I would like an important & Williams, 1995). job where people look up to me”). Participants were then exposed to a series of ten same-sex individuals who were either thin or heavy Future Directions and Treatment in their photographs and came across as either Implications successful or unsuccessful in their alleged self-descriptions. After being exposed to thin, As noted in this chapter, numerous theories, successful targets, women who were high on including those that embrace an evolutionary status aspiration reported significantly worse perspective, have been offered as explanations body satisfaction and greater ineffectiveness for the prevalence of eating disorders. Each (i.e., a lack of control over their lives) than of the available theories has various limitations women who were low on status aspiration. and/or is unable to explain certain aspects of Together with perfectionism, body dissatisfaction eating disorders. The intrasexual competition and ineffectiveness have been implicated in the model appears to offer a comprehensive account development of bulimic symptoms (Bardone- of eating disorder etiology and maintenance; Cone, Abramson, Vohs, Heatherton, & Joiner, however, more empirical investigations of the 2006) and the maintenance and exacerbation of intrasexual competition model are needed to bulimic symptoms (Joiner, Heatherton, Rudd, & substantiate this theoretical framework and to Schmidt, 1997). Thus, together with the other further demonstrate its precision and predictive findings, these results suggest that intrasexual power compared to existing frameworks. competitiveness is a significant factor that It will also be important for future work underlies the development of modern-day eating on the intrasexual competition model to incor- disorders. porate biological factors. Given recent findings, In summary, an intrasexual competition model which have found associations with disordered provides a promising evolutionary account for eating and hormonal factors both prenatally the development of disordered eating behaviors. (e.g., Quinton, Smith, & Joiner, 2011; Smith It addresses several of the shortcomings of et al., 2010) and at puberty (Klump et al., the other evolutionary hypotheses and is largely 2012), it will be informative for future work to consistent with the demographic profile of investigate the ovulatory cycle. Because women affected individuals and much of the other are more likely to accentuate their physical research on eating disorders, including the well- appearance during ovulation (Durante, Li, & established links between media consumption Haselton, 2008; Haselton, Mortezaie, Pillsworth, and women’s body image and eating attitudes. Bleske-Recheck, & Frederick, 2007), it may be The model has also been supported by various that women are especially likely to indicate investigations that have both correlationally and restrictive eating attitudes in response to cues of experimentally demonstrated the link between status competition around the time of ovulation. 340 N.P. Li et al.

It will also be important for future work intervention group, which consisted of watching to continue to investigate potential moderators, a movie about the realities of female images in like achievement motivation, and situational the media and participating in exercises and factors, like power, that may activate intrasexual discussions to increase media literacy, evidenced competition motives. For instance, as women less awareness of the thin ideal and greater continue to enter the global economy in record body satisfaction as compared to the control numbers (Aguirre, Sabbagh, Rupp, & Hoteit, group. Further, the effects of media literacy 2012), power may be a particularly salient factor programs have been found to persist long term. to examine with respect to disordered eating, as Specifically, Wilksch and Wade (2009) found power has been found to activate goal pursuits that after participating in an eight-session media (e.g., Galinsky, Gruenfeld, & Magee, 2003; literacy program, adolescent girls had signi- Kunstman & Maner, 2011). Thus, success in ficantly lower shape and weight concerns, the workforce could have potentially negative dieting concerns, body dissatisfaction, feelings downstream consequences among women whose of ineffectiveness, and depression at post- goals include dieting and weight loss. intervention and at a 30-month follow-up. The current review also provides suggestions Dissonance-based approaches, which are based for eating disorder treatment and prevention on Festinger’s cognitive dissonance theory (1957), efforts. Given that the abundance of idealized ask participants to take a counter-attitudinal media images is believed to over-activate stance against the thin ideal and have also intrasexual competition motives, and given that been found to be highly effective at reducing individuals are likely to continue to be increa- eating disorder-related cognitions and behaviors singly bombarded by such images, interventions, (Becker, Smith, & Ciao, 2006; Stice, Chase, such as media literacy programs, may be partic- Stormer, & Appel, 2001;Yager & O’Dea, 2008). ularly indicated for the prevention of eating For example, Stice, Shaw, Burton, and Wade disorders. These programs are designed to teach (2006) found that individuals in the dissonance- participants to be informed consumers of media based program had lower thin-ideal internaliza- and typically include psychoeducational compo- tion, dieting, and eating pathology symptoms nents and the viewing of presentations on the at a 1-year follow-up compared to assessment treatment of media images (e.g., utilizing techni- only controls. Thus, interventions that combine ques such as air brushing and Photoshopping media literacy and dissonance approaches may to make images look more “perfect”). Media be particularly effective in the prevention of dis- literacy programs are based on inoculation the- ordered eating. ory; specifically, they operate under the assum- ption that by providing participants with facts about advertising and media images, participants Conclusion will be less susceptible to thin ideal internalization In conclusion, eating restriction is a highly and the pressure to be thin (Wilksch, Durbridge, & nuanced phenomenon that has been viewed Wade, 2008). Further, it is hypothesized that from many perspectives and linked to many reducing susceptibility to internalization of the different factors. The intrasexual competition thin ideal will improve body image and decrease model has been especially promising, and behaviors that are associated with the develop- further examination is needed on the intra- ment of eating disorders, such as dieting (Yager sexual competition processes among people & O’Dea, 2008). afflicted with disordered eating. Such infor- Recent studies provide support for the effec- mation would prove useful for the develop- tiveness of media literacy programs in reducing ment of prevention and intervention programs eating disorder-related cognitions. For instance, that utilize an understanding of both the Watson and Vaughn (2006) found that the female ancient, adaptive mechanisms that underlie college students who took part in a 4-week eating restriction and the proximate factors 17 Intrasexual Competition and Other Theories of Eating Restriction 341

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