How common are eating disorders and what are the risks?

Eating disorders have been part of the psychiatric literature for many years; however, only in the past two decades have they commanded widespread interest in psychology, psychiatry, and allied professions. Part of the reason for this interest has been the recognition of the severe health consequences of the disorders; anorexia nervosa (AN) has a long and established history of high mortality, having an estimated mortality that is 12 times higher than expected and mortality rates are consistently ranked the highest of any other psychiatric disorder. Mortality rates for bulimia nervosa (BN) are much lower, but still notable. The prevalence rates of eating disorders in Western cultures are the topic of some debate; however, most epidemiological studies point to prevalence of 0.3% for AN and 1% for BN among young women.

Are the medical complcations a serious concern?

Medical complications are typical during the acute phase of an eating disorder and persist among those not successfully treated.  Eating disorders additionally are associated with a wide range of physical and emotional disorders through early adulthood, including major depression, OCD, substance abuse and anxiety. The complex interplay between psychological and physical symptoms argues against defining eating disorders as exclusively "psychiatric" or "medical" since effective treatment must target both domains.

Diagnosis

The prevailing diagnostic systems, the Diagnostic and Statistical Manual of Mental Disorders (4th ed. [DSM-IV]; American Psychiatric Association, 1994) and the International Classification of Diseases (World Health Organization, 1992) have limited current classifications of eating disorders to one of three diagnostic categories: that of AN, BN, and a third category of disorders not matching stringent criteria for either, labeled eating disorders not otherwise specified (EDNOS).  AN individuals have further been classified into subtypes of those who simply restrict caloric intake (AN-R) and those who have symptoms of binging and/or purging (AN-B/P).  Binge eating disorder (BED), characterized by binge eating episodes and lack of compensatory behaviors for caloric intake, is currently classified under EDNOS; however, it is likely to be addressed in more detail in the forthcoming edition of the DSM.

Despite merits of diagnostic classifications, the clinical stability of eating disorder diagnoses have been questioned in the long-term due to significant crossover between both diagnostic categories and subtypes.  While there is some distinctiveness between the categories of AN and BN diagnoses, the remarkable heterogeneity in psychological features within diagnostic subgroups underscores the clinical utility of evaluating patients on a broad spectrum of meaningful psychosocial variables.  For clinical purposes, there is far greater conceptual value in directly assessing psychological domains that are conceptually relevant across all eating disorder subgroups rather than simply drawing inferences from DSM-IV (1994)diagnostic categories.

Risk and Maintaining Factors

The understanding of factors that cause and maintain eating disorders has advanced substantially in recent decades.  Most models assume that eating disorders have multiple causes and vary tremendously in their presentation.  It is believed that the variations represent the interplay of three broad classes of predisposing or risk factors: cultural, individual, and familial. More recent scientific evidence, however, has begun to specify in greater detail the respective roles of these categories.

Cultural Factors:

Excessive restrictive dieting can prompt eating disorders in people who do not have underlying personality or family disturbances. It has been increasingly recognized that dieting can play a direct role in causing serious symptoms such as depression and binge-eating. Why do many women and an increasing number of men try to reduce their overall food intake?

For decades now, women have been bombarded with the message that they must diet in order to meet standards for beauty represented by ultra-thin fashion models. Thinness in women has become a symbol for beauty, success, happiness and self-control in our culture. Unfortunately, the idealized body shape for women is almost impossible for most people to achieve because it is completely contrary to biological and inherited factors that determine body weight. This conflict between fashion industry ideals and biological reality has led to a disturbing situation where most young women are incredibly dissatisfied with their body and feel they are too fat.

Family Factors:

There have also been theories suggesting that the family may play a role in the development and maintenance of anorexia nervosa. Some have suggested that families of those with the disorder tend to be overprotective, rigid, and suffocating in their closeness. In these cases, anorexia nervosa develops as a struggle for independence, autonomy, and individuality. It is likely to surface in adolescence when the individual, her parents, or the entire family are forced to deal with the new demands for independence and mature functioning. It must be emphasized that most of the descriptions of families have been based on observations made after anorexia nervosa has developed and, thus, they may reflect a response to a serious illness rather than an underlying cause of the disorder. The reason why this issue is so important is that parents often experience overwhelming feelings of guilt once they recognize that one of their children has an eating disorder.

While in some cases, family relationships may contribute to an anorexia nervosa, in other instances, it occurs in families that appear to be functioning well before the eating disorder has developed. Regardless, it is important to remember that an eating disorder is tremendously disruptive to the family and distress by all family members can be expected. Even when serious family dysfunction is present, it would be a serious error for either sufferers or their families to blame themselves for the eating disorder since it virtually never reflects some sort of deliberate wrongdoing on anyone's part.

There is some evidence that other family factors may increase the vulnerability to anorexia nervosa. For example, if one member of the family has the eating disorder, it is more likely to occur in other family members. It has also been suggested that a family history of depression or alcohol abuse may increase the likelihood of anorexia nervosa. Finally, there is evidence indicating that sexual abuse may increase the chance of an eating disorder developing.

In sum, the family can play a role in the development or the maintenance of a anorexia nervosa but it is also possible for an eating disorder to develop in families that were functioning well prior to the development of the eating disorder. In either case, blaming the sufferer or the family is inappropriate. As will be described later, the family can play a very important role in recovery.

Individual Factors:

People may be vulnerable to eating disorders either because of their psychological makeup or biological susceptibility. There have been many theories regarding psychological or personality attributes that may increase the risk of eating disorders. It has been suggested that those who develop the disorder may have difficulties in adapting to the host of sexual and social demands associated with adolescence. According to this view, self-starvation becomes a mechanism for avoiding maturity because it results in a return to pre-pubertal appearance and hormonal status. This regression is thought to provide relief from adolescent turmoil and conflicts for sufferers and their families. This explanation of anorexia nervosa should not be generalized to all cases since it only applies to a subgroup of sufferers.

Other factors that have been identified as leading to eating disorders are low self-esteem, feelings of ineffectiveness, poor body image, depression, emotional instability, rigid thinking patterns, and perfectionism. Particularly within the context of overall a poor self-image, the experience of self-control, virtue, and even power derived from success in weight control may lead a person to persist in weight loss efforts, even when it becomes obvious to others that this behavior is inappropriate. Those with anorexia nervosa often appear emotionally "driven" not only toward weight loss, but also in other areas of their life such as schoolwork, physical fitness, or career.

Unfortunately, a problem in determining which traits may cause eating disorders is that weight loss itself causes certain psychological disturbances to develop. Thus, some traits that have been observed in anorexia nervosa may be a consequence, rather than a cause, of the disorder.

It has been suggested that eating disorders may represent a form of "addictive" disorder and that certain foods should thus be avoided. Although there are parallels between anorexia nervosa and chemical dependency, there is little evidence that eating disorders are actually related to "addiction." Of greatest importance is that many of the treatment recommendations that come from the "addiction model" of eating disorders are ineffective and others may even be harmful.

There is some evidence indicating that genetics may play a role in eating disorders. For example, it is more likely that an eating disorder will develop in one identical twin if the other twin has the disorder. This is in contrast to fraternal twins (not identical) who have about the same risk of developing anorexia nervosa as do same-sex siblings. This may reflect some underlying biological vulnerability to eating disorders or it may indicate that being an identical twin presents particular psychological challenges that raise the likelihood of the observed association (e.g., competitiveness, difficulties in developing a separate identity). There have been other speculations regarding biological vulnerability to eating disorders but the evidence for this is not compelling at this time.

The Effects of Starvation on Behavior: Implications for Eating Disorders

One of the most important advancements in the understanding of eating disorders is the recognition that severe and prolonged dietary restriction can lead to serious physical and psychological complications (Garner, 1997). Many of the symptoms once thought to be primary features of anorexia nervosa are actually symptoms of starvation. Given what we know about the biology of weight regulation, what is the impact of weight suppression on the individual? This is particularly relevant for those with anorexia nervosa, but is also important for people with eating disorders who have lost significant amounts of body weight. Perhaps the most powerful illustration of the effects of restrictive dieting and weight loss on behavior is an experimental study conducted almost 50 years ago and published in 1950 by Ancel Keys and his colleagues at the University of Minnesota (Keys et al., 1950). The experiment involved carefully studying 36 young, healthy, psychologically normal men while restricting their caloric intake for 6 months. More than 100 men volunteered for the study as an alternative to military service; the 36 selected had the highest levels of physical and psychological health, as well as the most commitment to the objectives of the experiment. What makes the "starvation study" (as it is commonly known) so important is that many of the experiences observed in the volunteers are the same as those experienced by patients with eating disorders. This section of this chapter is a summary of the changes observed in the Minnesota study.

During the first 3 months of the semistarvation experiment, the volunteers ate normally while their behavior, personality, and eating patterns were studied in detail. During the next 6 months, the men were restricted to approximately half of their former food intake and lost, on average, approximately 25% of their former weight. Although this was described as a study of "semistarvation," it is important to keep in mind that cutting the men's rations to half of their former intake is precisely the level of caloric deficit used to define "conservative" treatments for obesity (Stunkard, 1993). The 6 months of weight loss were followed by 3 months of rehabilitation, during which the men were gradually refed. A subgroup was followed for almost 9 months after the re-feeding began. Most of the results were reported for only 32 men, since 4 men were withdrawn either during or at the end of the semistarvation phase. Although the individual responses to weight loss varied considerably, the men experienced dramatic physical, psychological, and social changes. In most cases, these changes persisted during the rehabilitation or re-nourishment phase.

Attitudes and Behavior Related to Food and Eating

One of the most of the striking changes that occurred in the volunteers was a dramatic increase in food preoccupations. The men found concentration on their usual activities increasingly difficult, because they became plagued by incessant thoughts of food and eating. During the semistarvation phase of the experiement, food became a principal topic of conversation, reading, and daydreams. Rating scales revealed that the men experienced an increase in thinking about food, as well as corresponding declines in interest in sex and activity during semistarvation. The actual words used in the original report are particularly revealing and the following quotations followed by page numbers in parentheses are from Keys et al. (1950) with permission of the University of Minnesota Press.

As starvation progressed, the number of men who toyed with their food increased. They made what under normal conditions would be weird and distasteful concoctions, (p. 832). . . Those who ate in the common dining room smuggled out bits of food and consumed them on their bunks in a long-drawn-out ritual, (p. 833). . . Toward the end of starvation some of the men would dawdle for almost two hours after a meal which previously they would have consumed in a matter of minutes, (p. 833). . . Cookbooks, menus, and information bulletins on food production became intensely interesting to many of the men who previously h ad little or no interest in dietetics or agriculture, (p. 833). [The volunteers] often reported that they got a vivid vicarious pleasure from watching other persons eat or from just smelling food. (p. 834)

In addition to cookbooks and collecting recipes, some of the men even began collecting coffeepots, hot plates, and other kitchen utensils. According to the original report, hoarding even extended to non-food-related items such as "old books, unnecessary second-hand clothes, knick knacks, and other 'junk.' Often after making such purchases, which could be afforded only with sacrifice, the men would be puzzled as to why they had bought such more or less useless articles" (p. 837). One man even began rummaging through garbage cans. This general tendency to hoard has been observed in starved anorexic patients (Crisp, Hsu, & Harding, 1980) and even in rats deprived of food (Fantino & Cabanac, 1980). Despite little interest in culinary matters prior to the experiment, almost 40% of the men mentioned cooking as part of their postexperiment plans. For some, the fascination was so great that they actually changed occupations after the experiment; three became chefs, and one went into agriculture!

The Minnesota subjects were often caught between conflicting desires to gulp their food down ravenously and consume it slowly so that the taste and odor of each morsel would be fully appreciated. Toward the end of starvation some of the men would dawdle for almost two hours over a meal which previously they would have consumed in a matter of minutes. . .they did much planning as to how they would handle their day's allotment of food. (p. 833) The men demanded that their food be served hot, and they made unusual concoctions by mixing foods together, as noted above. There was also a marked increase in the use of salt and spices. The consumption of coffee and tea increased so dramatically that the men had to be limited to 9 cups per day; similarly, gum chewing became excessive and had to be limited after it was discovered that one man was chewing as many as 40 packages of gum a day and "developed a sore mouth from such continuous exercise" (p. 835).

During the 12-week refeeding phase of the experiment, most of the abnormal attitudes and behaviors in regard to food persisted. A small number of men found that their difficulties in this area were quite severe during the first 6 weeks of refeeding:

Binge Eating

During the restrictive dieting phase of the experiment, all of the volunteers reported increased hunger. Some appeared able to tolerate the experience fairly well, but for others it created intense concern and led to a complete breakdown in control. Several men were unable to adhere to their diets and reported episodes of binge eating followed by self-reproach. During the eighth week of starvation, one volunteer flagrantly broke the dietary rules, eating several sundaes and malted milks; he even stole some penny candies. He promptly confessed the whole episode, [and] became self-deprecatory" (p. 884). While working in a grocery store, another man suffered a complete loss of will power and ate several cookies, a sack of popcorn, and two overripe bananas before he could "regain control" of himself. He immediately suffered a severe emotional upset, with nausea, and upon returning to the laboratory he vomited. . .He was self-deprecatory, expressing disgust and self-criticism. (p. 887)

One man was released from the experiment at the end of the semistarvation period because of suspicions that he was unable to adhere to the diet. He experienced serious difficulties when confronted with unlimited access to food "He repeatedly went through the cycle of eating tremendous quantities of food, becoming sick, and then starting all over again" (p. 890). During the refeeding phase of the experiment, many of the men lost control of their appetites and "ate more or less continuously" (p. 843).

Even after 12 weeks of refeeding, the men frequently complained of increased hunger immediately following a large meal.

[One of the volunteers] ate immense meals (a daily estimate of 5,000-6,000 cal.) and yet started "snacking" an hour after he finished a meal. [Another] ate as much as he could hold during the three regular meals and ate snacks in the morning, afternoon and evening. (p. 846). Several men had spells of nausea and vomiting. One man required aspiration and hospitalization for several days. (p. 843)

During the weekends in particular, some of the men found it difficult to stop eating. Their daily intake commonly ranged between 8,000 and 10,000 calories, and their eating patterns were described as follows:

Subject No. 20 stuffs himself until he is bursting at the seams, to the point of being nearly sick and still feels hungry; No. 120 reported that he had to discipline himself to keep from eating so much as to become ill; No. 1 ate until he was uncomfortably full; and subject No. 30 had so little control over the mechanics of "piling it in" that he simply had to stay away from food because he could not find a point of satiation even when he was "full to the gills.". . ."I ate practically all weekend," reported subject No. 26. . .Subject No. 26 would just as soon have eaten six meals instead of three. (p. 847)

After about 5 months of refeeding, the majority of the men reported some normalization of their eating patterns, but for some the extreme overconsumption persisted "No. 108 would eat and eat until he could hardly swallow any more and then he felt like eating half an hour later" (p. 847). More than 8 months after renourishment began, most men had returned to normal eating patterns; however, a few were still eating abnormal amounts "No. 9 ate about 25 percent more than his pre-starvation amount; once he started to reduce but got so hungry he could not stand it" (p. 847).

Factors distinguishing men who rapidly normalized their eating from those who continued to eat prodigious amounts were not identified. Nevertheless, the main findings here are as follows: Serious binge eating developed in a subgroup of men, and this tendency persisted in some cases for months after free access to food was reintroduced; however, the majority of men reported gradually returning to eating normal amounts of food after about 5 months of refeeding. Thus, the fact that binge eating was experimentally produced in some of these normal young men should temper speculations about primary psychological disturbances as the cause of binge eating in patients with eating disorders. These findings are supported by a large body of research indicating that habitual dieters display marked overcompensation in eating behavior that is similar to the binge eating observed in eating disorders (Polivy & Herman, 1985, 1987; Wardle & Beinart, 1981). Polivy et al., (1994) compared a group of former World War II prisoners of war and non-interned veterans and found that the former prisoners lost an average of 10.5 Kg. They also reported a significantly higher frequency of binge eating than non-interned veterans according to a self-report questionnaire sent by mail.

Emotional and Personality Changes

The experimental procedures involved selecting volunteers who were the most physically and psychologically robust. "The psychobiological 'stamina' of the subjects was unquestionably superior to that likely to be found in any random or more generally representative sample of the population" (pp. 915-916).

Although the subjects were psychologically healthy prior to the experiment, most experienced significant emotional deterioration as a result of semistarvation. Most of the subjects experienced periods during which their emotional distress was quite severe; almost 20% experienced extreme emotional deterioration that markedly interfered with their functioning. Depression became more severe during the course of the experiment. Elation was observed occasionally, but this was inevitably followed by "low periods." Mood swings were extreme for some of the volunteers:

[One subject] experienced a number of periods in which his spirits were definitely high. . . These elated periods alternated with times in which he suffered "a deep dark depression." (p. 903)

Irritability and frequent outbursts of anger were common, although the men had quite tolerant dispositions prior to starvation. For most subjects, anxiety became more evident. As the experiment progressed, many of the formerly even-tempered men began biting their nails or smoking because they felt nervous. Apathy also became common, and some men who had been quite fastidious neglected various aspects of personal hygiene. During semistarvation, two subjects developed disturbances of "psychotic" proportions. During the refeeding period, emotional disturbance did not vanish immediately but persisted for several weeks, with some men actually becoming more depressed, irritable, argumentative, and negativistic than they had been during semistarvation. After two weeks of refeeding, one man reported his extreme reaction in his diary:

I have been more depressed than ever in my life. . .I thought that there was only one thing that would pull me out of the doldrums, that is release from C.P.S. [the experiment] I decided to get rid of some fingers. Ten days ago, I jacked up my car and let the car fall on these fingers. . .It was premeditated. (pp. 894-895)

Several days latter, this man actually did chop off three fingers of one hand in response to the stress.

Standardized personality testing with the Minnesota Multiphasic Personality Inventory (MMPI) revealed that semistarvation resulted in significant increases on the Depression, Hysteria, and Hypochondriasis scales. The MMPI profiles for a small minority of subjects confirmed the clinical impression of incredible deterioration as a result of semistarvation. One man who scored well within normal limits at initial testing, but after 10 weeks of semistarvation and a weight loss of only about 4.5 kg (10 pounds, or approximately 7% of his original body weight), gross personality disturbances were evident on the MMPI. Depression and general disorganization were particularly striking consequences of starvation for several of the men who became the most emotionally disturbed.

Social and Sexual Changes

The extraordinary impact of semistarvation was reflected in the social changes experienced by most of the volunteers. Although originally quite gregarious, the men became progressively more withdrawn and isolated. Humor and the sense of comradeship diminished amidst growing feelings of social inadequacy. The volunteers' social contacts with women also declined sharply during semistarvation. Those who continued to see women socially found that the relationships became strained. These changes are illustrated in the account from one man's diary:

I am one of about three or four who still go out with girls. I fell in love with a girl during the control period but I see her only occasionally now. It's almost too much trouble to see her even when she visits me in the lab. It requires effort to hold her hand. Entertainment must be tame. If we see a show, the most interesting part of it is contained in scenes where people are eating. (p. 853)

Sexual interests were likewise drastically reduced. Masturbation, sexual fantasies, and sexual impulses either ceased or became much less common. One subject graphically stated that he had "no more sexual feeling than a sick oyster." (Even this peculiar metaphor made reference to food.) Keys et al. observed that "many of the men welcomed the freedom from sexual tensions and frustrations normally present in young adult men" (p. 840). The fact that starvation perceptibly altered sexual urges and associated conflicts is of particular interest, since it has been hypothesized that this process is the driving force behind the dieting of many anorexia nervosa patients. According to Crisp (1980), anorexia nervosa is an adaptive disorder in the sense that it curtails sexual concerns for which the adolescent feels unprepared. During rehabilitation, sexual interest was slow to return. Even after 3 months, the men judged themselves to be far from normal in this area. However, after 8 months of renourishment, virtually all of the men had recovered their interest in sex.

Cognitive and Physical Changes

The volunteers reported impaired concentration, alertness, comprehension, and judgment during semistarvation; however, formal intellectual testing revealed no signs of diminished intellectual abilities. As the 6 months of semistarvation progressed, the volunteers exhibited many physical changes, including gastrointestinal discomfort; decreased need for sleep; dizziness; headaches; hypersensitivity to noise and light; reduced strength; poor motor control; edema (an excess of fluid causing swelling); hair loss; decreased tolerance for cold temperatures (cold hands and feet); visual disturbances (i.e., inability to focus, eye aches, "spots" in the visual fields); auditory disturbances (i.e., ringing noise in the ears); and paresthesias (i.e., abnormal tingling or prickling sensations, especially in the hands or feet).

Various changes reflected an overall slowing of the body's physiological processes. There were decreases in body temperature, heart rate, and respiration, as well as in basal metabolic rate (BMR). BMR is the amount of energy (in calories) that the body requires at rest (i.e., no physical activity) in order to carry out normal physiological processes. It accounts for about two-thirds of the body's total energy needs, with the remainder being used during physical activity. At the end of semistarvation, the men's BMRs had dropped by about 40% from normal levels. This drop, as well as other physical changes, reflects the body's extraordinary ability to adapt to low caloric intake by reducing its need for energy. More recent recent research has shown that metabolic rate is markedly reduced even among dieters who do not have a history of dramatic weight loss (Platte, Wurmser, Wade, Mecheril & Pirke, 1996). During refeeding, Keys et al. found that metabolism speeded up, with those consuming the greatest number of calories experiencing the largest rise in BMR. The group of volunteers who received a relatively small increment in calories during refeeding (400 calories more than during semistarvation) had no rise in BMR for the first 3 weeks. Consuming larger amounts of food caused a sharp increase in the energy burned through metabolic processes.

Significance of the "starvation Study"

As is readily apparent from the preceding description of the Minnesota experiment, many of the symptoms that might have been thought to be specific to anorexia nervosa and bulimia nervosa are actually the results of starvation (Pirke & Ploog, 1987). These are not limited to food and weight, but extend to virtually all areas of psychological and social functioning. Since many of the symptoms that have been postulated to cause these disorders may actually result from undernutrition, it is absolutely essential that weight be returned to "normal" levels so that psychological functioning can be accurately assessed.

The profound effects of starvation also illustrate the tremendous adaptive capacity of the human body and the intense biological pressure on the organism to maintain a relatively consistent body weight. This makes complete evolutionary sense. Over hundreds of thousands of years of human evolution, a major threat to the survival of the organism was starvation. If weight had not been carefully modulated and controlled internally, early humans most certainly would simply have died when food was scarce or when their interest was captured by countless other aspects of living. The Keys et al. "starvation study" illustrates how the human being becomes more oriented toward food when starved and how other pursuits important to the survival of the species (e.g., social and sexual functioning) become subordinate to the primary drive toward food.

One of the most notable implications of the Minnesota experiment is that it challenges the popular notion that body weight is easily altered if one simply exercises a bit of "willpower." It also demonstrates that the body is not simply "reprogrammed" at a lower set point once weight loss has been achieved. The volunteers' experimental diet was unsuccessful in overriding their bodies' strong propensity to defend a particular weight level. Again, it is important to emphasize that following the months of refeeding, the Minnesota volunteers did not skyrocket into obesity. On the average, they gained back their original weight plus about 10%; then, over the next 6 months, their weight gradually declined. By the end of the follow-up period, they were approaching their preexperiment weight levels.

Providing patients with eating disorders with the above account of the semistarvation study can be very useful in giving them an "explanation" for many of the emotional, cognitive and behavioral symptoms that they experience. This as well as other educational materials (Garner, 1997) is based on the assumption that eating disorder patients often suffer from misconceptions about the factors that cause and then maintain symptoms. It is further assumed that patients may be less likely to persist in self-defeating symptoms if they are made truly aware of the scientific evidence regarding factors that perpetuate eating disorders. The educational approach conveys the message that the responsibility for change rests with the patient; this is aimed at increasing motivation and reducing defensiveness. The operating assumption is that the patient is a responsible and rational partner in a collaborative relationship.

Adapted from:

Garner, D.M. (1997). Psychoeducational principles in the treatment of eating disorders. In: Handbook for Treatment of Eating Disorders. (145-177). D.M. Garner & P.E. Garfinkel (Eds). New York, NY: Guilford Press.

Download article summarizing the Starvation Study: Garner, D.M. (1998) The effects of starvation on behavior: Implications for dieting and eating disorders, Healthy Weight Journal, 68-72.

References:

Crisp, A. J. (1980)). Anorexia Nervosa: Let me be. London: Academic Press.

Crisp, A. H., Hsu, L. K. G., & Harding, B. (1980). The starving hoarder and voracious spender: Stealing in anorexia nervosa. Journal of Psychosomatic Research, 24, 225-231.

Garner, D.M. (1997). Psychoeducational principles in the treatment of eating disorders. In: Handbook for Treatment of Eating Disorders (pp. 145-177), D.M. Garner & P.E. Garfinkel (Eds). New York, NY: Guilford Press.

Fantino, M., & Cabanac, M. (1980). Body weight regulation with a proportional hoarding response in the rat. Physiology and Behavior, 24, 939-942.

Keys, A., Brozek, J., Henschel, A., Mickelsen, O., & Taylor, H. L. (1950). The biology of human starvation (2 vols.). Minneapolis: University of Minnesota Press.

Pirke, K. M., & Ploog, D. (1987). Biology of human starvation. In P. J. V. Beumont, G. D. Burrows, & R. C. Casper (Eds.), Handbook of eating disorders: Part 1 Anorexia and bulimia nervosa (pp. 79-102). New York: Elsevier.

Platte, P., Wurmser, H., Wade, S. E., Mecheril, A., & Pirke, K. M. (1996). Resting metabolic rate and diet-induced thermogenesis in restrained and unrestrained eaters. International Journal of Eating Disorders, 20, 33-41.

Polivy, J., Zeitlin, S.B., Herman, C.P. & Beal, A.L. (1994). Food restriction and binge eating: A study of former prisioners of war. Journal of Abnormal Psychology, 103, 409-411.

Polivy, J., & Herman, C.P. (1985). Dieting and bingeing: A causal analysis. American Psychologist, 40, 193-201.

Polivy, J., & Herman, C. P. (1987). Diagnosis and treatment of normal eating. Journal of Consulting and Clinical Psychology, 55, 635-644.

Stunkard, A. J. (1993). Introduction and overview. In A. J. Stunkard & T. A. Wadden (Eds.), Obesity: Theory and therapy (2nd Ed., pp. 1-10). New York: Raven Press.

Wardle, J., & Beinart, H. (1981). Binge eating: A theoretical review. British Journal of Clinical Psychology, 19-20, 97-109.