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 following is a summary of this experiment published previously: Garner, D. M. (1998). The effects of starvation on behavior: Implications for dieting and eating disorders. Healthy Weight Journal, 12(5), 68-72.
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.
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 experiment, 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 semi-starvation. 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 post-experiment 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:
The extraordinary impact of semi-starvation 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.
The volunteers reported impaired concentration, alertness, comprehension, and judgment during semi-starvation; however, formal intellectual testing revealed no signs of diminished intellectual abilities. As the 6 months of semi-starvation 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.
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 pre-experiment weight levels.
Providing patients with eating disorders with the above account of the semi-starvation 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.
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