A Big Fat Crisis (6 page)

In a similar experiment, conducted by social psychologists Kathleen Vohs and Todd Heatherton, thirty-six women considered chronic dieters were asked to watch an emotional scene from the movie
Terms of Endearment
.
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Half were asked to control their emotions and suppress their feelings, while the other half were asked to act naturally. After the movie the subjects participated in an ice cream taste test. They were told to eat as much ice cream as they wanted. Those who had
been asked to suppress their emotions ate 55 percent more ice cream than those who had been asked to act naturally. Controlling emotions appeared to deplete their ability to exercise self-control immediately afterward, and they ended up gorging on the ice cream.

Several studies have even suggested that people who attempt to diet run the risk of getting even fatter over the long run. Another twin study—one following Finnish twins over twenty-five years—convincingly demonstrated this unintended consequence.
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Researchers followed 4,129 individual twins, most of whom were born from 1975 to 1979. The twins who made a concerted effort to lose at least ten pounds ran a greater risk of becoming overweight. By comparing the weight differences between monozygotic and dizygotic twins, one of whom tried to lose weight while the other didn’t (comparing the genetic factors versus nongenetic factors), they found that although a large part of the weight gain appeared to be genetic, a smaller portion was attributable to dieting itself.

In today’s world, dieting and its many demands are beyond the capacity of most. It is not just hard manual labor that tires us. Decision-making, thinking, concentrating, and exerting self-control to resist food use up our limited mental energy. Having too many options, whether it’s the variety of snacks, candy bars, or breakfast cereals that take up entire aisles in supercenters, can make decisions more difficult, sometimes leading to cognitive overload and poor choices.
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And the available options continue to multiply on a daily basis.

Our ability to make active, thoughtful decisions is a type of self-control. It fatigues, but it can be renewed after rest. When we exhaust our reserves, we typically function on “default,” hardwired behaviors that automatically lead us to the “easy” choices that do not require self-control. When it comes to energy balance, our default behaviors are to eat as much as we can when food is available, and to rest as much as we can when we don’t have to be physically active to obtain food.

Glucose, the sugar in our blood that supplies calories to our cells and organs, plays an important role in self-control. When we make careful, thoughtful decisions and control our impulsive behaviors, we burn glucose. Per ounce of body weight, our brain consumes more
sugar than any other organ in the body. It constitutes 2 percent of body mass but consumes 20–25 percent of the body’s calories.
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In another study of self-control, one group of sixty subjects was given a drink of lemonade made with real sugar, while another group of sixty participants was provided with lemonade made with an artificial sweetener with no calories. Afterward, half the participants in each of the two groups were asked to perform a task that required self-control, to avoid looking at distracting words on a video monitor. All 120 participants were then asked to make some choices that depended on thoughtful reasoning. Those who got the lemonade with real sugar made the best choices, and those who were served the lemonade with artificial sweetener did the worst.
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The work required by the self-control task depleted the brain’s cognitive-processing capacity, handicapping those whose blood sugar was not replenished.

Cognitive, controlled, effortful processes like those for decision-making and dealing with novel situations appear to be highly susceptible to fluctuations in glucose. The change in blood glucose is quite subtle. In a similar lemonade study the glucose level of each participant before being asked to control eye gaze and not look at distracting words was, on average, 107 mg/dL. After doing the task, the average glucose level fell to 101 mg/dL.
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As a doctor I would say there is no clinically significant difference between those two levels of glucose, and that both represent a normally functioning pancreas and insulin response. Yet these subtle differences distinguished those with higher performances from those with lower. This phenomenon is likely to explain why children who eat breakfast do better in school than those who skip it. One study showed that the sooner children took tests after they were fed, the better they did.
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The irony is that the more someone tries to control herself by avoiding tempting food, the more the brain uses up the available sugar and the more difficult it is to continue to exercise self-control. The lower our blood sugar is, the more likely we are to choose foods high in sugar and fat. Any one instance of self-control is relatively easy, but it appears that continuous demands for self-control will be self-defeating.

Likewise, when shopping, we are constantly comparing and making
trade-offs, since we have to choose one item over another. The number and difficulty of the choices we have to make affect how depleted and vulnerable we will become. When we make larger trade-offs, we tend to become more mentally fatigued. For instance, in one study, participants were asked to choose between two different memory sticks and then select a snack, a chocolate chip cookie or a yogurt. After making a large trade-off by choosing between a relatively cheap, low-capacity 64MB memory stick and an expensive, high-capacity 3GB one, study participants were more likely to choose a chocolate chip cookie over a yogurt than participants who were asked to choose between memory sticks that differed only slightly in price and storage capacity.
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Yet irrespective of the magnitude of the trade-offs, the more choices we have to make in a short period of time, the more depleted we become and the more vulnerable we are to temptations.
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Maintaining self-control when shopping may be especially challenging for people with a low income. Dean Spears, a Princeton University PhD candidate, conducted an experiment in India in which he randomized participants to be “rich” or “poor.”
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(By American standards of income, all the participants would be considered very poor.) Those in the “rich” group could choose two of three items, which they could have for free, while those in the “poor” group could choose only one for free. Afterward, all the participants were asked to squeeze a handgrip for as long as they could—a test of self-control. The rich group significantly outlasted the poor group. Spears also had a control group in which “poor” and “rich” participants were randomly assigned to receive one or two items, but they did not get to make the choice themselves. Their performance on the self-control tests was significantly better than that of the “poor” participants who had to make the choice themselves.

For decades, economists have recognized that being poor is associated with more self-control challenges. The demands of large trade-offs and the subsequent depletion of self-control may be among the mechanisms that explain, in part, why low-income groups have higher rates of obesity. If you have only $10, for example, and what you want to buy costs $15, you have to give something up. Having to make difficult
trade-offs is highly depleting, leaving individuals more vulnerable to automatic, impulsive behaviors. This difficulty has nothing to do with character or personality—it is situational.

Regardless of whether people are rich or poor, to lose a substantial amount of weight, people need to resist food multiple times per day, rule out many options, and make large trade-offs every day of the week, every week of the year, for many years. In the current environment, with temptations everywhere, the mental effort needed to lose weight is enormous.

For most, dieting will not be the answer to weight control. Dieting will be frustrating and disappointing. It’s clear that the few, who seem to be able to completely change their lifestyle, lose weight, and keep it off, are pretty exceptional. If it were easy and common, we wouldn’t need testimonials that a diet program worked.

A dieter’s eating behavior tends to become abnormal over time, usually after some experience with successful self-control at the beginning of the effort. As dieting continues, the desire to eat may become greater, although dieters show no differences in the actual enjoyment of food compared to nondieters.
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Dieters will usually go through periods when, instead of inhibiting their eating, they break down and eat too much, certainly more than a person who isn’t dieting would eat in the same circumstance. Some dieters call the lapses in self-control “what-the-hell” reasoning—if they experience a single lapse, they may let go completely and find themselves bingeing.
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There are other downsides to applying self-control for weight loss. Many people who are dieting have been found to have trouble making decisions, and they tend to perform poorly on tests of executive capacity.
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If we improve self-control in one area, we often sacrifice it in another area. That is why people who try to quit smoking often gain weight. By directing their limited capacity for self-control toward refusing cigarettes, smokers have less capacity to refuse food.
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Similarly, if we try to control something like our emotions, we might not be able to refuse alcohol.

The physiological constraints of what our brains can handle cannot be easily altered. There are limits as to how many decisions, choices,
challenges, and stresses we can actively address in one day. The advice not to sweat the small stuff allows us to marshal our limited resources for the important decisions.

When you think about it, it seems obvious that our ability to exert self-control for long periods of time is limited.
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At some point, we can no longer hold up a weight, stay alert, or continue to move. We need to rest. We need to relax. We need a break. It takes energy to resist, to fight, and to refuse. The energy to maintain self-control has to come from somewhere, and when we use it to withstand the forces that cause us to eat too much, we deplete our energy reserves and have less energy available for other activities and tasks.
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And it isn’t just our efforts to avoid or resist food that deplete our reserves of willpower. Controlling our emotions when interacting with demanding partners, refraining from making impulse purchases, and abstaining from sexual behavior or drug and alcohol use can all deplete our self-control and lead us to make immediate, reflexive responses that preclude self-restraint.
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When we are depleted and have a choice between easy and difficult behaviors, we typically choose the one that is easiest and most convenient; that causes the least exertion, analysis, and work; and that provides the most immediate short-term pleasure or reward.

Could that be a doughnut or a Frappuccino?

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The Overwhelmed Brain

As we learned in the last chapter, the limits of self-control are key factors in our poor eating habits. One reason self-control is limited is because the capacity of the brain’s information-processing system is relatively minuscule.

Scientists generally agree that our brain has two operating systems: a cognitive system and a noncognitive system. The cognitive system requires conscious awareness; it is reflective and deliberate. It can perform mathematical computations, make novel decisions, and engage in long-term planning and “out-of-the-box” thinking.
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It operates, on average, less than 5 percent of the time and is the internal resource responsible for self-control.

The other 95 percent of the time, our noncognitive system is in control. Impulsive and immediate—and following well-established rules and patterns—it is responsible for quick, automatic decision-making. The noncognitive system is often emotionally charged and responds to external signals, cues, information, signs, or symbols. When a person is under stress, tired, preoccupied, or overwhelmed with too much information, noncognitive processing dominates over thoughtful decision-making.
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Put more simply, when we are overloaded, we tend to make decisions impulsively. And when it comes to food, impulsivity
typically leads to nutritionally poor choices and what we perceive as a loss of self-control.

We can think of our brain as being engaged in a constant ebb and flow between deliberate and automatic processing. Sometimes it is more of a fight between two mismatched warriors, like David and Goliath. David represents the small, nimble, and smart cognitive force that has to face a massive, primitive, noncognitive giant that is in charge most of the time. Goliath is unflagging and never sleeps. Sometimes David can win, but it is nearly impossible for him to win all the time. David can be distracted, he can be worn down, and he needs to sleep. This is not a single battle but an eternal struggle.

Limited Processing Capacity and Food Choices

To illustrate how the cognitive and noncognitive systems interrelate, psychologists Baba Shiv and Alexander Fedorikhin developed an experiment that looked at the kind of decisions people make when their cognitive systems are occupied (also called a “cognitive load”), compared to when they have less to think about.
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In this study 165 participants were asked to memorize either a two- or seven-digit number (the same length as a phone number without the area code). After they were shown the number briefly on an index card, they were asked to memorize it and then select a ticket for a snack, which was supposed to be a token reward for participating in the study. The participants got to choose either a piece of chocolate cake or a fruit salad. After they selected the ticket, they had to disclose the number they memorized and then complete a final questionnaire about the factors that influenced their choice of snack. Presented with the sentence “My final decision about which snack to choose was driven by . . .” they were asked to choose between “my thoughts or feelings,” “my willpower or desire,” “my prudent self or my impulsive self,” “the rational side or the emotional side,” and “my head or my heart.”