The Keys Semi-Starvation Study
Ancel Keys wanted to find out the physical and psychological effects of what happens to the human body when it starves and how it recovers from starvation. He thought his information would be useful if the soldiers were captured in the war and they reached the point of starvation.
Keys conducted a study to determine the effects of food restriction. His results were amazing. We know that restriction causes weight loss but look at all the other symptoms of the experiment. They are classic eating disorder symptoms. The study shows that restricting food affects us not only physically, but psychologically and behaviorally as well. Note that even after the subjects started eating normally the psychological and behavioral effects remained.
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 semi-starvation 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 “semi-starvation,” 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 Most of the results were reported for only 32 men, since 4 men were withdrawn either during or at the end of the semi-starvation phase.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 semi-starvation 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 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 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 re-feeding 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 re-feeding:
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 semi-starvation 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 re-feeding 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 re-feeding, 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 re-feeding, 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 come 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 re-feeding. 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 research indicating that habitual dieters display marked overcompensation in eating behaviors that are 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 semi-starvation. 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 semi-starvation, two subjects developed disturbances of “psychotic” proportions. During the re-feeding 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 semi-starvation. After two weeks of re-feeding, 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 later, 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 semi-starvation resulted in significant increases on the Depression, Hysteria, and Hpochondriasis scales. The MMPI profiles for a small minority of subjects confirmed the clinical impression of incredible deterioration as a result of semi-starvation. One man who scored well within normal limits at initial testing, but after 10 weeks of semi-starvation 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 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 semi-starvation. 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 a 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 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 semi-starvation, 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 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 re-feeding, 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 re-feeding (400 calories more than during semi-starvation) 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 re-feeding, 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.
Excerpts from the Handbook for the Treatment of Eating Disorders, D.M. Gardner and P.E. Garfinkel (editors), Gilford Press, New York, N.Y., 1997.
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. (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.
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