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Fat is a psychological issue - health - 16 November 1991 - New Scientist
This is a long article but has some very valid points, and is a very strong argument for following a healthy diet and having a flexible approach to dieting.
Fat is a psychological issue
16 November 1991 by PETER HERMAN and JANET POLIVY
Near the top of just about every Westerner's wish list is a slimmer figure. Exercise is a possibility, but the pain-to-gain (or pain-to-loss) ratio is uncomfortably high. Surgery is another approach, but it is not easily accessible, or even particularly reliable. That leaves dieting, the most widely adopted strategy. More people nowadays are watching their weight than ever before, and the benefits to health, appearance and self-esteem seem so obvious that one wonders why there is anyone who doesn't diet.
Of course, everyone is familiar with the difficulties of dieting. Every worthwhile diet demands sacrifices, and sacrifice is not something that comes naturally to most people. And then there is the well-known fact that most diets, while initially successful, quickly run out of steam. A few months later, dieters are likely to be back where they started. These are the problems of diet failure.
Just as important are the problems that plague even the successful dieter. We have found that dieters, whether successful or not, display pathologies of eating; their normal regulatory mechanisms are undermined. Indeed, the fact that their normal regulatory processes are compromised turns out to contribute to the overeating to which most dieters are prone, and which makes the eventual failure of the diet so likely. The demerits of dieting are not confined to eating behaviour, however. We have noted aberrations in the realms of emotion and cognition - broadly, how we feel and think about the world and ourselves - and these aberrations suggest that the dieter is under substantial stress.
This stress, along with the weight fluctuations that accompany the typical alternation of extended abstinence and ruinous overeating, even threatens the dieter's physical health. All in all, we regard dieting more as a problem than as a solution, and recommend extreme caution before embarking on what may well prove to be a counterproductive enterprise.
Our jaundiced view of dieting arises from a series of experiments that we have conducted on mostly female undergraduates in and around Chicago and Toronto. Initially, we were interested in the question of how people regulate their calorie intake; that is, how well people compensate for a particular 'preload' provided by the experimenter. In our first experiment, the preload was either one 7.5 ounce (210 gram) milk shake, two such milk shakes, or none. Immediately following this preload, our subjects were given three different flavours of ice cream to eat.
We presented the experiment as a study of taste perception. The subjects thought that they were merely sampling the ice cream - although while doing so they could eat as much of it as they wanted - and that we were interested in how the ice cream tasted to them after they had drunk a milk shake of a particular flavour.
The purpose of this deception was to convince subjects that we were not interested in how much ice cream they ate. For that reason, we secretly weighed the ice cream bowls before and after the students had eaten, to calculate their intake. We also made sure that these bowls contained ample ice cream, so that the students would not become self-conscious about consuming a great deal of it if they chose to. We also ensured that the subjects ate in absolute privacy.
At the end of the experiment, subjects completed a questionnaire that allowed us to divide them roughly in half into dieters and nondieters. The nondieters we tested behaved in a straightforward fashion: they ate less ice cream following one milk shake than following none, and still less following two milk shakes. This pattern should not surprise anyone. It simply indicates that people compensate for their prior consumption.
There is some dispute about whether this compensation is based on physiological feedback or on cognitive calculations of how much to eat. The physiological argument is that the caloric impact of the milk shake is registered in the bloodstream or hypothalamus, which in turn dictates less eating if recent in-take has been high.
Others, however, have argued that there is insufficient time in a study such as this for physiological feedback to be effective, so people compensate on the basis of their beliefs regarding how much they can or ought to eat. Whichever is true, nondieters do compensate.
For the dieters we tested, the results were surprising. Instead of compensating for the milk shake preloads, the dieters actually ate more ice cream following one or two milk shakes than after none at all. We labelled this phenomenon 'counter-regulation,' because it runs counter to normal regulation. This surprising pattern has been replicated a number of times in our laboratory as well as elsewhere. But what does it signify?
One possibility is that dieters have a contrary physiology. Perhaps the effect of the milkshake is to make them paradoxically hungrier and thus more likely to eat. People with such a physiology would almost certainly have to become dieters. We and others have been able to eliminate this possibility by producing the effect in studies in which all the subjects receive the same preload (such as pudding), but half of them are led to believe that the preload is high in calories, while the other half are told that the preload is low calorie.
Dieters eat more after the preload that they believe is high in calories, even if it is not. By contrast, nondieters eat slightly more after the preload labelled 'low calorie', incidentally lending some support to the notion that the compensation they show is at least partially based on their thoughts and beliefs.
Why then do dieters counter-regulate? We believe that this bizarre response arises from the nature of dieting itself. A formal definition of dieting is that it is an intentional inhibition of caloric intake in the pursuit of a slimmer physique.
This inhibition, however straightforward it may appear, produces a number of unintended and even counterproductive consequences. First, it demands that one's eating comes under deliberate control; no longer can one eat whenever one is hungry and the available food is tasty.
The natural controls of physiological feedback combined with learnt regulatory strategies that govern nondieters' eating are dangerous for the dieter. After all, these natu-ral controls have produced a physique that the dieter is evidently dissatisfied with - hence the diet. The alterna-tive is to gain deliberate control over one's eating. Dieters decide how much, and when, and what, they will eat, irrespective of their natural inclinations.
After extended practice in neglecting one's physiology in favour of one's conscious caloric agenda, the normal controls on eating eventually atrophy. We do not mean to suggest that food deprivation no longer produces a 'hunger' reaction in the bloodstream, but simply that this reaction no longer calls forth corrective measures at the behavioural level, that is, eating.
In effect, the dieter stops responding to hunger cues. For instance, when dieters start off without a milk shake, they then eat very little ice cream. Their diet is intact, and the fact that they might be hungry is no reason to eat. In the experimental condition in which subjects receive no milk shake, dieters eat considerably less ice cream than do nondieters.
But why do dieters over-eat after consuming a milk shake? Doesn't that overeating directly conflict with their dietary resolve? Certainly it does, but our research indicates that the effect of the milk shake - and here perhaps is the paradox - undermines the dieters' resolve, temporarily releasing them from their vows of abstinence. After the milk shake, instead of doing penance for the caloric sin, the dieter persists in sinful indulgence. After all, if staying on one's diet is no longer possible, then why not make the most of the situation?
The psychology of dieting hinges on the fact that dieters' ultimate goals of achieving or maintaining a slim physique - are long term, but their dieters' behaviour-control strategies are about as short-sighted as could be. Virtually all diets involve caloric allowances over short periods of time. Instead of allowing ourselves 730 000 calories over the course of the year, we allow ourselves 2000 calories a day (or more likely, 1500). Even this short-term allowance is usually broken down into more immediate units, such as 350 calories for breakfast, or 650 calories for dinner.
This segmentation of the diet has the advantage of making it clear what one can or cannot eat at any particular time, but it has the tremendous disadvantage of inflexibility. If the units of a diet are calories per meal, and those allowances are relatively ungenerous, it becomes all too easy to find one-self violating the diet.
For instance, what if you are in an experiment in which you are virtually forced to consume 7.5 ounces or even 15 ounces of milk shake? Such an event effectively blows the diet, and in response most dieters simply give up. Having failed to maintain their caloric virtue, they lapse into a state of perdition, in which ice cream represents a temptation to which they might as well yield, as the damage has already been done.
The psychology underlying this phenomenon is made clear by the fact that one need not actually exceed one's caloric quota in order to give up the diet and overindulge; one need only think that one has blown one's diet, as is clear from the study in which dieters who were told that the milk shake was fattening went on to overeat, whereas those who thought that it was low calorie maintained their customary rejection of ice cream. To further emphasise the psychological nature of diet-breaking, researchers have demonstrated that merely anticipating having to consume a high calorie milk shake will make dieters abandon their diet.
We believe this research accurately reflects the dynamics of real life. Much of our lives involves eating, and often this social eating involves being induced to 'just try' this or 'have some more' of that.
We eat because others around us are eating, as research in our own laboratory and elsewhere has amply demonstrated.
If we don't, we are often subjected to more explicit pressure to eat.
Our hosts will be disappointed, if not insulted.
The food will go to waste.
Restaurant and dinner party meals are often larger than necessary.
Our dining companions want us to join them (and not just watch them) eating.
All these elements conspire to induce dieters to eat when they know that they shouldn't; and once they have, the floodgates are open, and they tend to stay that way for some time.
Researchers have not yet looked systematically at how dieters regain control of themselves. The standard assumption - derived from dieters' own rationalisations - is that they will begin their diet again tomorrow morning, or perhaps on Monday; in any event, not tonight. The diet unit is most often the day - say, 1500 calories a day - so it 'makes sense' to rededicate one's diet when self-control and a concern for the future, intensified by remorse over one's past, greet the dawn.
On the night before the morning after, however, dieters' overindulgences may reach legendary proportions. The seeming inability of dieters to stop once they have truly started stems from the Faustian bargain that they made when they exchanged normal, physiologically based controls on eating for deliberate cognitive controls. As was noted above, those normal controls tend to atrophy; included in the wastage are the processes normally involved in registering satiety. Dieters do not eat interminably once their diets are broken, but they often eat much more than nondieters ever do.
Although exceeding one's caloric quota is a good way to break one's diet, there are many other routes to dietary breakdown.
Just as dieters may be misled into thinking that a particular amount of milk shake is too rich and therefore calorically excessive, so dieters, displaying the convoluted 'logic' for which they are notable, may convince themselves that one particular type of calorie is more of a threat to their diet than some other type.
For instance, in one study, dieters overate ice cream following a milk shake, but dieters given a mixture of cottage cheese and fruit salad equivalent in calories to the milk shake did not overeat. In the mind of the dieter, a bowl of cottage cheese and fruit salad does not violate a diet, no matter how many calories it may contain, whereas certain foods - such as milk shakes - will break a diet even in quite small quantities.
This sort of 'magical thinking' is fostered by many popular diets that confer special powers on certain foods: they are said to promote weight loss by virtue of nutritional mechanisms that operate independently of their caloric content.
Salads are diet foods, while forbidden food, such as milk shakes, cakes, sweets and sometimes even bread can demolish a diet even in minute amounts. If this sort of diet logic escapes you, remember that these same dieters also believe that once your diet is blown, 2000 calories of overindulgence is not much worse than 500, and that the slate will be clean in the morning.
The threats to one's dietary virtue considered so far involve caloric overindulgence that breeds on itself. But there are other reasons for abandoning a diet. There is now a considerable literature which shows that dieters tend to overeat when they are distressed. Nondieters tend to respond to distress by eating less, owing to the physiological concomitants of distress, such as the activation of the autonomic nervous system, which in turn elevates blood sugar levels and decreases hunger.
When people are distressed, one of the first things that goes is their commitment to long-term goals. They tend to shorten their sights, and lose control of their behaviour to powerful stimuli in the immediate environment. Customary inhibitions are loosened. Dieters, as we have seen, are largely oblivious to hunger as a guide for eating; instead, they rely on their dietary resolve. With their resolved weakened, dieters faced with attractive food will eat it.
Many clinicians have interpreted as functional the overeating by fat people and other dieters when they are distressed: food or eating, they claim, serves to combat distress. Considerable research has failed to unearth any evidence for this; on the contrary, most dieters admit to feeling even worse once they acknowledge that they have added caloric insult to the original injury.
Admittedly, it remains difficult to determine with any precision exactly how dieters are feeling while they are in the middle of a binge. Overeating may temporarily take their minds off their troubles, and asking them how they feel may serve merely to remind them that they have plenty to be upset about. Our preference, however, is to view distress-induced overeating not as a source of emotional comfort but as a result of a shift in the control of behaviour.
The unperturbed dieter adheres to a long-term agenda of restraint, whereas agitated dieters cannot see beyond the irresistible temptations before them.
The same sort of process may well apply to anybody who chronically attempts to inhibit any sort of behaviour. Distress may make it difficult to say no to smoking, taking drugs or engaging in acts of aggression.
All these behaviours are ordinarily under control, but people who are upset and no longer focused on the long-term consequences of their actions may find them irresistible. We believe that intoxicants such as alcohol similarly tend to undermine dieters' resolve by reducing their attention to long-term consequences, leaving them prey to immediate temptations.
The psychology of dieting is a struggle for control. Dieting demands self-control, but the world conspires to interfere, with the result that dieting has come to be known as a 'losing battle'. Dieters more often than not end up yo-yoing: weight fluctuates as periods of successful abstinence are cancelled out by bouts of capitulation to forbidden food. Indeed, there is mounting evidence that the periods of indulgence may more than compensate for the periods of abstinence.
Dieters' bodies may even actively defend the weight that so troubles the dieter. As weight is lost, various alterations occur that make it more difficult to lose more weight, and much easier to put weight on again.
Most people are familiar with the sad fact that weight loss triggers a slowing of metabolic rate so that it takes fewer calories to support normal activities. Weight loss proceeds reasonably well at first on most diets, but eventually grinds to a frustrating halt. This is largely due to the fact that our bodies adjust to a lower weight by shifting to a thrifty metabolism that in effect squeezes more energy out of each calorie consumed.
At the same time other defensive adjustments make continued weight loss difficult or impossible. Significant weight loss breeds lethargy, which in its way contributes to the body's effort to restore its weight to a higher level. Weight loss alters our reaction to food as well.
Michel Cabanac has documented a phenomenon he calls 'negative alliesthesia', a decrease in the pleasantness of sweets following a meal or caloric load. Ordinarily, we all exhibit negative alliesthesia; after a rich meal, our preference for sweets is less that it was before the meal.
But people who have lost weight do not show the negative alliesthesia reaction; their sweet preference remains high. In one study, Cabanac and two of his colleagues each lost about 10 per cent of their body weight to prove the point. Cabanac interprets this sweet tooth reaction as defensive in nature: the body is trying to seduce its owner into excessive indulgence - of sweet, calorically dense foods - so that the lost weight may be restored.
Finally, there is a wealth of evidence that dieters' attempts to resist food produce a countervailing pressure in the form of obsessive thinking about food. The most notable study in this regard involved a number of conscientious objectors during the Second World War who voluntarily lost almost a quarter of their body weight. Their minds, as a consequence, came to be monopolised by thoughts of food, including fantasies of gourmet meals past and to come, and plans for their future career as chefs.
These obsessions are considered to be the mental equivalent of the physiological and perceptual defences trying to make the underweight individual eat if possible. Note that the food thoughts produced by hunger are about the sensual attractions of food, and not about food's caloric threat to the waistline.
All the foregoing reactions have been interpreted as natural defences, designed to promote eating in people who are eating less than they should. Of course, some people who are eating less than they should may have no alternative: our world contains many more genuinely starving people than dieters. If a starving person's metabolism slows down, that may prolong life.
And starving people are likely to lower their threshold of acceptability for particular foods, occasionally eating substances that we would not normally consider edible.
But starving people do not usually need convincing; they are more than ready to comply with the nutritional demands of their bodies, if only food were to become available. Dieters, by contrast, are intent on resisting food, and resisting the weight-restoring defences erected by their bodies. They are engaged in a conflict that is opposite to that of the starving person: the dieter wants to eat less than the environment provides.
This conflict at the heart of dieting is a source of continual stress. As well as making it difficult to maintain control over eating, this stress has other, more remote effects.
Dieters regularly score higher than nondieters on measures of emotional agitation; in the laboratory, they tend to overreact to emotional provocation. Also, dieters are more easily distracted when performing certain mental tasks, such as proofreading, and are more likely to show impairment of mental performance when they are observed by others. All these effects are consistent with the argument that dieters are in a chronically stressed state.
We have become so accustomed to dieting that the notion of deliberate undereating no longer seems to require explanation.
But when we observe the defensive reactions with which our physiology combats deliberate undereating, and when we consider the evolutionary heritage that makes undereating a threat to our wellbeing, then perhaps we are entitled to question the wisdom of dieting.
Let us begin by examining the reasons that people offer for undertaking dieting in the first place. Until recently, the major problem facing people was how to obtain enough food. Just a century ago, our great grandparents' only concern was that their children be sufficiently stout. The dramatic extension of people's lifespan over the past century has had the ironic effect of bringing to the fore diseases that most people in earlier times did not live long enough to die from.
Heart disease and other diseases thought to be associated with being overweight must in this sense be considered luxury diseases. The actuaries who work in the insurance industry have provided us with 'ideal weights' which allegedly minimise the risks of disease and death.
You can now be too fat: a report published in 1985 from the US National Institutes of Health decreed that in general Americans were too fat for their own good. Even as little as five excess pounds may pose a serious health risk, the report suggested. No wonder dieting has become a national preoccupation in the US.
The case against being overweight, however, is not as clear as one might imagine. Many of the alleged health consequences of excess weight are merely correlations; they have not been shown to be caused by excess weight per se.
More interestingly, recent evidence suggests that dieting itself may impair one's health, especially if dieting results in wide weight swings, which is the typical pattern. Thus, when fat people are judged actuarially to be at greater risk, we must ask whether the dieting that often accompanies their obesity contributes significantly to that risk.
Of course, health concerns are not the only reason for dieting. Many dieters - perhaps most - are at least equally concerned about their appearance, and strenuous dieting is still the main method for losing those unsightly bulges. But why is slimness considered more attractive than fatness? When we ask this question of our friends and relatives, we are usually met with a look of incredulity that seems specially designed for academics who persist in their obtuseness. It is evident to almost everyone that the overweight are aesthetically unappealing; beauty and ugliness require no explanation beyond their manifestation.
We remain uncertain as to the source of the aesthetic derogation of fatness, and the corresponding idealisation of slimness. We are not short of suggestions. Perhaps we value what is rare; nowadays, slimness is increasingly in short supply, whereas in the days of Rubens's well-endowed nudes a little extra flesh had a rare and special allure. Perhaps one's manifest physique is an index of prestige: whereas in feudal times only the lords could afford to feast, now it is only the well-off who can afford a week at a health farm.
Beyond health and attractiveness, dieters often gain a sense of personal satisfaction from dieting - often from just deciding to diet - because dieting represents an explicit commitment to self-improvement and confers a feeling that one has taken control over at least one facet of one's life. One is reminded of the Protestant ethic - and, perversely, of Ambrose Bierce's definition of an abstainer as 'a weak person who yields to the temptation of denying himself a pleasure'.
All the reasons that impel individuals to diet are reinforced socially. The medical profession is strongly and vocally committed to decrying the perils of overweight, and doctors are often inclined to blame various ills on excess weight itself - and then blame the overweight person for being overweight. The fashion and entertainment industries likewise have little use for the overweight. Media stars are notable for their idealised physical appearance; whatever else women have liberated themselves from, they remain subject to the tyranny of looking good - and that means slim. Our culture generally displays widespread prejudice against the wide-spread. 'Fat' jokes are tolerated where jokes regarding other individual characteristics or disabilities would not be. One of the first epithets learned in the school playground is 'fat', and schoolchildren in one study showed a stronger aversion to being obese than to being blind or physically crippled.
Recent years have seen attempts to combat prejudice against overweight people. The National Association to Advance Fat Acceptance in the US publishes a newsletter, holds conventions, monitors the media and assists in legal proceedings intended to overcome prejudice. Magazines directed to fat women are marketed. But like most liberation movements, fat liberation has had to reconcile two contradictory impulses: fat people's desires to be accepted as they are, and fat people's desire to become slim, or at least not fat. Some headway has been made in raising consciousness about the damage that prejudicial attitudes cause, but the battle has barely begun, and fat people remain socially stigmatised.
From the psychological point of view, perhaps the most interesting feature of dieting - one that helps to explain both society's aversion to fat and the tremendous difficulty fat people have in losing weight - is the ambiguity of weight control. The diet industry, worth tens of billions of dollars a year, has as its premise the notion that people can lose weight. It also adds its voice to the chorus suggesting that people should lose weight, but that chorus hardly needs additional support.
Much of the research on dieting and dieters, however, suggests that the attempt to lose weight is likely to fail, that deliberate restriction of one's food intake is, while obviously possible, nevertheless a precarious endeavour. As we have already seen, dietary restraint is subject to all sorts of disruptions. The allure of food is constantly threatening to break through and take control. Abstinence can all too quickly become unrestrained gorging, and the effect of these high calorie lapses is exacerbated by physiological defences that incline the body toward weight gain.
Although the past two decades have seen increasing media attention to the biological basis of weight, to the idea that the weight that we naturally attain may be a reflection of our underlying physiology, perhaps even our genetics, there is still insufficient attention paid to the difficulties and costs of weight reduction. Admittedly, weight reduction is possible; this evident fact makes it difficult to argue for a simple-minded interpretation of obesity in which weight is simply fixed by our genes.
Weight is not fixed, but it is apparently defended, and dieters who attempt to overcome those defences are going to have to pay a price. Substituting a diet for normal physiological controls on eating leads ultimately to counter-regulation and disinhibition. Even those who do succeed in losing some weight find that the struggle intensifies as their weight declines. Dieters' battle is with their own bodies; and to this point, matter has the upper hand on mind.
For many years, overweight has been regarded as a problem to which dieting is the solution. Now it is clear that being 'overweight' cannot necessarily be viewed as a disorder; it may well be a perfectly natural state for some people. Dieting, in fact, may be more of an insult to nature. Certainly nature takes its revenge physiologically and psychologically on most dieters.
This argument is not equivalent to an endorsement of the notion that nothing must be restricted. But at the same time, we must remember that the ideal is by definition neither too much nor too little. Diet consciousness - with its paroxysms of logic, its attempt to subject the body to the whims of fashion, and its persistent stress and frustrations - continues to cause at least as many problems as it solves.
It is no accident that the major eating disorders - anorexia nervosa and bulimia nervosa - are invariably preceded by strenuous dieting. The normal psychology of dieting is simply a template for the abnormal psychology of eating disorders. And the symptoms of eating disorders - alternating abstinence and bingeing, emotional volatility, magical and disoriented thinking, low self-esteem and the pervasive pursuit of slimness - are all writ small in everyday dieting.
Peter Herman and Janet Polivy are professors in the psychology department of the University of Toronto.
This is a long article but has some very valid points, and is a very strong argument for following a healthy diet and having a flexible approach to dieting.
Fat is a psychological issue
16 November 1991 by PETER HERMAN and JANET POLIVY
Near the top of just about every Westerner's wish list is a slimmer figure. Exercise is a possibility, but the pain-to-gain (or pain-to-loss) ratio is uncomfortably high. Surgery is another approach, but it is not easily accessible, or even particularly reliable. That leaves dieting, the most widely adopted strategy. More people nowadays are watching their weight than ever before, and the benefits to health, appearance and self-esteem seem so obvious that one wonders why there is anyone who doesn't diet.
Of course, everyone is familiar with the difficulties of dieting. Every worthwhile diet demands sacrifices, and sacrifice is not something that comes naturally to most people. And then there is the well-known fact that most diets, while initially successful, quickly run out of steam. A few months later, dieters are likely to be back where they started. These are the problems of diet failure.
Just as important are the problems that plague even the successful dieter. We have found that dieters, whether successful or not, display pathologies of eating; their normal regulatory mechanisms are undermined. Indeed, the fact that their normal regulatory processes are compromised turns out to contribute to the overeating to which most dieters are prone, and which makes the eventual failure of the diet so likely. The demerits of dieting are not confined to eating behaviour, however. We have noted aberrations in the realms of emotion and cognition - broadly, how we feel and think about the world and ourselves - and these aberrations suggest that the dieter is under substantial stress.
This stress, along with the weight fluctuations that accompany the typical alternation of extended abstinence and ruinous overeating, even threatens the dieter's physical health. All in all, we regard dieting more as a problem than as a solution, and recommend extreme caution before embarking on what may well prove to be a counterproductive enterprise.
Our jaundiced view of dieting arises from a series of experiments that we have conducted on mostly female undergraduates in and around Chicago and Toronto. Initially, we were interested in the question of how people regulate their calorie intake; that is, how well people compensate for a particular 'preload' provided by the experimenter. In our first experiment, the preload was either one 7.5 ounce (210 gram) milk shake, two such milk shakes, or none. Immediately following this preload, our subjects were given three different flavours of ice cream to eat.
We presented the experiment as a study of taste perception. The subjects thought that they were merely sampling the ice cream - although while doing so they could eat as much of it as they wanted - and that we were interested in how the ice cream tasted to them after they had drunk a milk shake of a particular flavour.
The purpose of this deception was to convince subjects that we were not interested in how much ice cream they ate. For that reason, we secretly weighed the ice cream bowls before and after the students had eaten, to calculate their intake. We also made sure that these bowls contained ample ice cream, so that the students would not become self-conscious about consuming a great deal of it if they chose to. We also ensured that the subjects ate in absolute privacy.
At the end of the experiment, subjects completed a questionnaire that allowed us to divide them roughly in half into dieters and nondieters. The nondieters we tested behaved in a straightforward fashion: they ate less ice cream following one milk shake than following none, and still less following two milk shakes. This pattern should not surprise anyone. It simply indicates that people compensate for their prior consumption.
There is some dispute about whether this compensation is based on physiological feedback or on cognitive calculations of how much to eat. The physiological argument is that the caloric impact of the milk shake is registered in the bloodstream or hypothalamus, which in turn dictates less eating if recent in-take has been high.
Others, however, have argued that there is insufficient time in a study such as this for physiological feedback to be effective, so people compensate on the basis of their beliefs regarding how much they can or ought to eat. Whichever is true, nondieters do compensate.
For the dieters we tested, the results were surprising. Instead of compensating for the milk shake preloads, the dieters actually ate more ice cream following one or two milk shakes than after none at all. We labelled this phenomenon 'counter-regulation,' because it runs counter to normal regulation. This surprising pattern has been replicated a number of times in our laboratory as well as elsewhere. But what does it signify?
One possibility is that dieters have a contrary physiology. Perhaps the effect of the milkshake is to make them paradoxically hungrier and thus more likely to eat. People with such a physiology would almost certainly have to become dieters. We and others have been able to eliminate this possibility by producing the effect in studies in which all the subjects receive the same preload (such as pudding), but half of them are led to believe that the preload is high in calories, while the other half are told that the preload is low calorie.
Dieters eat more after the preload that they believe is high in calories, even if it is not. By contrast, nondieters eat slightly more after the preload labelled 'low calorie', incidentally lending some support to the notion that the compensation they show is at least partially based on their thoughts and beliefs.
Why then do dieters counter-regulate? We believe that this bizarre response arises from the nature of dieting itself. A formal definition of dieting is that it is an intentional inhibition of caloric intake in the pursuit of a slimmer physique.
This inhibition, however straightforward it may appear, produces a number of unintended and even counterproductive consequences. First, it demands that one's eating comes under deliberate control; no longer can one eat whenever one is hungry and the available food is tasty.
The natural controls of physiological feedback combined with learnt regulatory strategies that govern nondieters' eating are dangerous for the dieter. After all, these natu-ral controls have produced a physique that the dieter is evidently dissatisfied with - hence the diet. The alterna-tive is to gain deliberate control over one's eating. Dieters decide how much, and when, and what, they will eat, irrespective of their natural inclinations.
After extended practice in neglecting one's physiology in favour of one's conscious caloric agenda, the normal controls on eating eventually atrophy. We do not mean to suggest that food deprivation no longer produces a 'hunger' reaction in the bloodstream, but simply that this reaction no longer calls forth corrective measures at the behavioural level, that is, eating.
In effect, the dieter stops responding to hunger cues. For instance, when dieters start off without a milk shake, they then eat very little ice cream. Their diet is intact, and the fact that they might be hungry is no reason to eat. In the experimental condition in which subjects receive no milk shake, dieters eat considerably less ice cream than do nondieters.
But why do dieters over-eat after consuming a milk shake? Doesn't that overeating directly conflict with their dietary resolve? Certainly it does, but our research indicates that the effect of the milk shake - and here perhaps is the paradox - undermines the dieters' resolve, temporarily releasing them from their vows of abstinence. After the milk shake, instead of doing penance for the caloric sin, the dieter persists in sinful indulgence. After all, if staying on one's diet is no longer possible, then why not make the most of the situation?
The psychology of dieting hinges on the fact that dieters' ultimate goals of achieving or maintaining a slim physique - are long term, but their dieters' behaviour-control strategies are about as short-sighted as could be. Virtually all diets involve caloric allowances over short periods of time. Instead of allowing ourselves 730 000 calories over the course of the year, we allow ourselves 2000 calories a day (or more likely, 1500). Even this short-term allowance is usually broken down into more immediate units, such as 350 calories for breakfast, or 650 calories for dinner.
This segmentation of the diet has the advantage of making it clear what one can or cannot eat at any particular time, but it has the tremendous disadvantage of inflexibility. If the units of a diet are calories per meal, and those allowances are relatively ungenerous, it becomes all too easy to find one-self violating the diet.
For instance, what if you are in an experiment in which you are virtually forced to consume 7.5 ounces or even 15 ounces of milk shake? Such an event effectively blows the diet, and in response most dieters simply give up. Having failed to maintain their caloric virtue, they lapse into a state of perdition, in which ice cream represents a temptation to which they might as well yield, as the damage has already been done.
The psychology underlying this phenomenon is made clear by the fact that one need not actually exceed one's caloric quota in order to give up the diet and overindulge; one need only think that one has blown one's diet, as is clear from the study in which dieters who were told that the milk shake was fattening went on to overeat, whereas those who thought that it was low calorie maintained their customary rejection of ice cream. To further emphasise the psychological nature of diet-breaking, researchers have demonstrated that merely anticipating having to consume a high calorie milk shake will make dieters abandon their diet.
We believe this research accurately reflects the dynamics of real life. Much of our lives involves eating, and often this social eating involves being induced to 'just try' this or 'have some more' of that.
We eat because others around us are eating, as research in our own laboratory and elsewhere has amply demonstrated.
If we don't, we are often subjected to more explicit pressure to eat.
Our hosts will be disappointed, if not insulted.
The food will go to waste.
Restaurant and dinner party meals are often larger than necessary.
Our dining companions want us to join them (and not just watch them) eating.
All these elements conspire to induce dieters to eat when they know that they shouldn't; and once they have, the floodgates are open, and they tend to stay that way for some time.
Researchers have not yet looked systematically at how dieters regain control of themselves. The standard assumption - derived from dieters' own rationalisations - is that they will begin their diet again tomorrow morning, or perhaps on Monday; in any event, not tonight. The diet unit is most often the day - say, 1500 calories a day - so it 'makes sense' to rededicate one's diet when self-control and a concern for the future, intensified by remorse over one's past, greet the dawn.
On the night before the morning after, however, dieters' overindulgences may reach legendary proportions. The seeming inability of dieters to stop once they have truly started stems from the Faustian bargain that they made when they exchanged normal, physiologically based controls on eating for deliberate cognitive controls. As was noted above, those normal controls tend to atrophy; included in the wastage are the processes normally involved in registering satiety. Dieters do not eat interminably once their diets are broken, but they often eat much more than nondieters ever do.
Although exceeding one's caloric quota is a good way to break one's diet, there are many other routes to dietary breakdown.
Just as dieters may be misled into thinking that a particular amount of milk shake is too rich and therefore calorically excessive, so dieters, displaying the convoluted 'logic' for which they are notable, may convince themselves that one particular type of calorie is more of a threat to their diet than some other type.
For instance, in one study, dieters overate ice cream following a milk shake, but dieters given a mixture of cottage cheese and fruit salad equivalent in calories to the milk shake did not overeat. In the mind of the dieter, a bowl of cottage cheese and fruit salad does not violate a diet, no matter how many calories it may contain, whereas certain foods - such as milk shakes - will break a diet even in quite small quantities.
This sort of 'magical thinking' is fostered by many popular diets that confer special powers on certain foods: they are said to promote weight loss by virtue of nutritional mechanisms that operate independently of their caloric content.
Salads are diet foods, while forbidden food, such as milk shakes, cakes, sweets and sometimes even bread can demolish a diet even in minute amounts. If this sort of diet logic escapes you, remember that these same dieters also believe that once your diet is blown, 2000 calories of overindulgence is not much worse than 500, and that the slate will be clean in the morning.
The threats to one's dietary virtue considered so far involve caloric overindulgence that breeds on itself. But there are other reasons for abandoning a diet. There is now a considerable literature which shows that dieters tend to overeat when they are distressed. Nondieters tend to respond to distress by eating less, owing to the physiological concomitants of distress, such as the activation of the autonomic nervous system, which in turn elevates blood sugar levels and decreases hunger.
When people are distressed, one of the first things that goes is their commitment to long-term goals. They tend to shorten their sights, and lose control of their behaviour to powerful stimuli in the immediate environment. Customary inhibitions are loosened. Dieters, as we have seen, are largely oblivious to hunger as a guide for eating; instead, they rely on their dietary resolve. With their resolved weakened, dieters faced with attractive food will eat it.
Many clinicians have interpreted as functional the overeating by fat people and other dieters when they are distressed: food or eating, they claim, serves to combat distress. Considerable research has failed to unearth any evidence for this; on the contrary, most dieters admit to feeling even worse once they acknowledge that they have added caloric insult to the original injury.
Admittedly, it remains difficult to determine with any precision exactly how dieters are feeling while they are in the middle of a binge. Overeating may temporarily take their minds off their troubles, and asking them how they feel may serve merely to remind them that they have plenty to be upset about. Our preference, however, is to view distress-induced overeating not as a source of emotional comfort but as a result of a shift in the control of behaviour.
The unperturbed dieter adheres to a long-term agenda of restraint, whereas agitated dieters cannot see beyond the irresistible temptations before them.
The same sort of process may well apply to anybody who chronically attempts to inhibit any sort of behaviour. Distress may make it difficult to say no to smoking, taking drugs or engaging in acts of aggression.
All these behaviours are ordinarily under control, but people who are upset and no longer focused on the long-term consequences of their actions may find them irresistible. We believe that intoxicants such as alcohol similarly tend to undermine dieters' resolve by reducing their attention to long-term consequences, leaving them prey to immediate temptations.
The psychology of dieting is a struggle for control. Dieting demands self-control, but the world conspires to interfere, with the result that dieting has come to be known as a 'losing battle'. Dieters more often than not end up yo-yoing: weight fluctuates as periods of successful abstinence are cancelled out by bouts of capitulation to forbidden food. Indeed, there is mounting evidence that the periods of indulgence may more than compensate for the periods of abstinence.
Dieters' bodies may even actively defend the weight that so troubles the dieter. As weight is lost, various alterations occur that make it more difficult to lose more weight, and much easier to put weight on again.
Most people are familiar with the sad fact that weight loss triggers a slowing of metabolic rate so that it takes fewer calories to support normal activities. Weight loss proceeds reasonably well at first on most diets, but eventually grinds to a frustrating halt. This is largely due to the fact that our bodies adjust to a lower weight by shifting to a thrifty metabolism that in effect squeezes more energy out of each calorie consumed.
At the same time other defensive adjustments make continued weight loss difficult or impossible. Significant weight loss breeds lethargy, which in its way contributes to the body's effort to restore its weight to a higher level. Weight loss alters our reaction to food as well.
Michel Cabanac has documented a phenomenon he calls 'negative alliesthesia', a decrease in the pleasantness of sweets following a meal or caloric load. Ordinarily, we all exhibit negative alliesthesia; after a rich meal, our preference for sweets is less that it was before the meal.
But people who have lost weight do not show the negative alliesthesia reaction; their sweet preference remains high. In one study, Cabanac and two of his colleagues each lost about 10 per cent of their body weight to prove the point. Cabanac interprets this sweet tooth reaction as defensive in nature: the body is trying to seduce its owner into excessive indulgence - of sweet, calorically dense foods - so that the lost weight may be restored.
Finally, there is a wealth of evidence that dieters' attempts to resist food produce a countervailing pressure in the form of obsessive thinking about food. The most notable study in this regard involved a number of conscientious objectors during the Second World War who voluntarily lost almost a quarter of their body weight. Their minds, as a consequence, came to be monopolised by thoughts of food, including fantasies of gourmet meals past and to come, and plans for their future career as chefs.
These obsessions are considered to be the mental equivalent of the physiological and perceptual defences trying to make the underweight individual eat if possible. Note that the food thoughts produced by hunger are about the sensual attractions of food, and not about food's caloric threat to the waistline.
All the foregoing reactions have been interpreted as natural defences, designed to promote eating in people who are eating less than they should. Of course, some people who are eating less than they should may have no alternative: our world contains many more genuinely starving people than dieters. If a starving person's metabolism slows down, that may prolong life.
And starving people are likely to lower their threshold of acceptability for particular foods, occasionally eating substances that we would not normally consider edible.
But starving people do not usually need convincing; they are more than ready to comply with the nutritional demands of their bodies, if only food were to become available. Dieters, by contrast, are intent on resisting food, and resisting the weight-restoring defences erected by their bodies. They are engaged in a conflict that is opposite to that of the starving person: the dieter wants to eat less than the environment provides.
This conflict at the heart of dieting is a source of continual stress. As well as making it difficult to maintain control over eating, this stress has other, more remote effects.
Dieters regularly score higher than nondieters on measures of emotional agitation; in the laboratory, they tend to overreact to emotional provocation. Also, dieters are more easily distracted when performing certain mental tasks, such as proofreading, and are more likely to show impairment of mental performance when they are observed by others. All these effects are consistent with the argument that dieters are in a chronically stressed state.
We have become so accustomed to dieting that the notion of deliberate undereating no longer seems to require explanation.
But when we observe the defensive reactions with which our physiology combats deliberate undereating, and when we consider the evolutionary heritage that makes undereating a threat to our wellbeing, then perhaps we are entitled to question the wisdom of dieting.
Let us begin by examining the reasons that people offer for undertaking dieting in the first place. Until recently, the major problem facing people was how to obtain enough food. Just a century ago, our great grandparents' only concern was that their children be sufficiently stout. The dramatic extension of people's lifespan over the past century has had the ironic effect of bringing to the fore diseases that most people in earlier times did not live long enough to die from.
Heart disease and other diseases thought to be associated with being overweight must in this sense be considered luxury diseases. The actuaries who work in the insurance industry have provided us with 'ideal weights' which allegedly minimise the risks of disease and death.
You can now be too fat: a report published in 1985 from the US National Institutes of Health decreed that in general Americans were too fat for their own good. Even as little as five excess pounds may pose a serious health risk, the report suggested. No wonder dieting has become a national preoccupation in the US.
The case against being overweight, however, is not as clear as one might imagine. Many of the alleged health consequences of excess weight are merely correlations; they have not been shown to be caused by excess weight per se.
More interestingly, recent evidence suggests that dieting itself may impair one's health, especially if dieting results in wide weight swings, which is the typical pattern. Thus, when fat people are judged actuarially to be at greater risk, we must ask whether the dieting that often accompanies their obesity contributes significantly to that risk.
Of course, health concerns are not the only reason for dieting. Many dieters - perhaps most - are at least equally concerned about their appearance, and strenuous dieting is still the main method for losing those unsightly bulges. But why is slimness considered more attractive than fatness? When we ask this question of our friends and relatives, we are usually met with a look of incredulity that seems specially designed for academics who persist in their obtuseness. It is evident to almost everyone that the overweight are aesthetically unappealing; beauty and ugliness require no explanation beyond their manifestation.
We remain uncertain as to the source of the aesthetic derogation of fatness, and the corresponding idealisation of slimness. We are not short of suggestions. Perhaps we value what is rare; nowadays, slimness is increasingly in short supply, whereas in the days of Rubens's well-endowed nudes a little extra flesh had a rare and special allure. Perhaps one's manifest physique is an index of prestige: whereas in feudal times only the lords could afford to feast, now it is only the well-off who can afford a week at a health farm.
Beyond health and attractiveness, dieters often gain a sense of personal satisfaction from dieting - often from just deciding to diet - because dieting represents an explicit commitment to self-improvement and confers a feeling that one has taken control over at least one facet of one's life. One is reminded of the Protestant ethic - and, perversely, of Ambrose Bierce's definition of an abstainer as 'a weak person who yields to the temptation of denying himself a pleasure'.
All the reasons that impel individuals to diet are reinforced socially. The medical profession is strongly and vocally committed to decrying the perils of overweight, and doctors are often inclined to blame various ills on excess weight itself - and then blame the overweight person for being overweight. The fashion and entertainment industries likewise have little use for the overweight. Media stars are notable for their idealised physical appearance; whatever else women have liberated themselves from, they remain subject to the tyranny of looking good - and that means slim. Our culture generally displays widespread prejudice against the wide-spread. 'Fat' jokes are tolerated where jokes regarding other individual characteristics or disabilities would not be. One of the first epithets learned in the school playground is 'fat', and schoolchildren in one study showed a stronger aversion to being obese than to being blind or physically crippled.
Recent years have seen attempts to combat prejudice against overweight people. The National Association to Advance Fat Acceptance in the US publishes a newsletter, holds conventions, monitors the media and assists in legal proceedings intended to overcome prejudice. Magazines directed to fat women are marketed. But like most liberation movements, fat liberation has had to reconcile two contradictory impulses: fat people's desires to be accepted as they are, and fat people's desire to become slim, or at least not fat. Some headway has been made in raising consciousness about the damage that prejudicial attitudes cause, but the battle has barely begun, and fat people remain socially stigmatised.
From the psychological point of view, perhaps the most interesting feature of dieting - one that helps to explain both society's aversion to fat and the tremendous difficulty fat people have in losing weight - is the ambiguity of weight control. The diet industry, worth tens of billions of dollars a year, has as its premise the notion that people can lose weight. It also adds its voice to the chorus suggesting that people should lose weight, but that chorus hardly needs additional support.
Much of the research on dieting and dieters, however, suggests that the attempt to lose weight is likely to fail, that deliberate restriction of one's food intake is, while obviously possible, nevertheless a precarious endeavour. As we have already seen, dietary restraint is subject to all sorts of disruptions. The allure of food is constantly threatening to break through and take control. Abstinence can all too quickly become unrestrained gorging, and the effect of these high calorie lapses is exacerbated by physiological defences that incline the body toward weight gain.
Although the past two decades have seen increasing media attention to the biological basis of weight, to the idea that the weight that we naturally attain may be a reflection of our underlying physiology, perhaps even our genetics, there is still insufficient attention paid to the difficulties and costs of weight reduction. Admittedly, weight reduction is possible; this evident fact makes it difficult to argue for a simple-minded interpretation of obesity in which weight is simply fixed by our genes.
Weight is not fixed, but it is apparently defended, and dieters who attempt to overcome those defences are going to have to pay a price. Substituting a diet for normal physiological controls on eating leads ultimately to counter-regulation and disinhibition. Even those who do succeed in losing some weight find that the struggle intensifies as their weight declines. Dieters' battle is with their own bodies; and to this point, matter has the upper hand on mind.
For many years, overweight has been regarded as a problem to which dieting is the solution. Now it is clear that being 'overweight' cannot necessarily be viewed as a disorder; it may well be a perfectly natural state for some people. Dieting, in fact, may be more of an insult to nature. Certainly nature takes its revenge physiologically and psychologically on most dieters.
This argument is not equivalent to an endorsement of the notion that nothing must be restricted. But at the same time, we must remember that the ideal is by definition neither too much nor too little. Diet consciousness - with its paroxysms of logic, its attempt to subject the body to the whims of fashion, and its persistent stress and frustrations - continues to cause at least as many problems as it solves.
It is no accident that the major eating disorders - anorexia nervosa and bulimia nervosa - are invariably preceded by strenuous dieting. The normal psychology of dieting is simply a template for the abnormal psychology of eating disorders. And the symptoms of eating disorders - alternating abstinence and bingeing, emotional volatility, magical and disoriented thinking, low self-esteem and the pervasive pursuit of slimness - are all writ small in everyday dieting.
Peter Herman and Janet Polivy are professors in the psychology department of the University of Toronto.
