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. 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. 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.
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. 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.”
Among participants who had to memorize the
two-digit number, 41 percent chose the chocolate cake, while among those
who memorized the seven-digit number, 63 percent chose chocolate cake, a
50 percent difference. Those who had to memorize the seven-digit number
said their decision was influenced more by their emotional, impulsive
side than by their rational, prudent side. The researchers concluded
that the group memorizing the longer number had less available
brainpower to carefully consider the items, and resorted to impulse.
Given
how taxed the average person is by the stresses of his or her job and
family life—stresses that far exceed having to memorize a seven-digit
number—our tendency to take mental shortcuts when it comes to figuring
out what to eat is understandable. Is it any wonder that we sometimes
choose cake over fruit? Before we do, does it cross our minds that one
bite of cake might have five times the calories of a bite of fruit?
Probably not.
The part of the brain that governs conscious
awareness is relatively small and processes only forty to sixty bits per
second, the equivalent of a short sentence. The brain’s entire
processing capacity, however, which includes the visual system as well
as the unconscious, automatic system, is estimated to process eleven
million bits per second. This is faster than a sophisticated computer
and about five hundred thousand times the power of our conscious
awareness.
To better appreciate how small our David is compared to
our Goliath, look at the grid in [the] Figure [below]. If this 50 × 50
grid represents the entire cognitive capacity of all the neurons of the
human brain (Goliath), the single dark square represents an amount
about two hundred times larger than the cognitive capacity of our
conscious awareness (David).
Why
is Goliath so large compared to David? Goliath has to direct all the
minutiae of every gesture, movement, action, and reaction. Goliath gets
us out of bed, moves our arms and legs just the right amount so we don’t
fall over, and alternates our fingers back and forth to efficiently
scratch that itch on our scalp. Goliath makes sure that when we walk
from the house to the car, we lift our feet just so high to ascend the
correct distance from the ground. When we get in the car, Goliath
ensures that we elegantly maneuver to a sitting position without bumping
our head, and that we find the brake and gas pedal. Goliath is
simultaneously processing all that our senses experience—the sights of
the road ahead, the sounds of the freeway, the smells of the new air
freshener, the aftertaste of coffee, the wind against our cheeks. As
Goliath is navigating the journey, David, however, is focused on a very
narrow set of goals: what to get Mom for Mother’s Day, which movie to
see this weekend, whether Goliath automatically locked the front door,
and whether David should go back home and check.
Distractions and Eating
Because
our cognitive capacity is so limited, most of us can do or think about
only one thing at a time. If we multitask, we can consciously direct
only one of the tasks, while the other is handled automatically.
In
an experiment conducted by French researchers France Bellisle and
Anne-Marie Dalix, a group of forty-one healthy, normal-weight women were
asked to come to the laboratory weekly for four weeks. The first week
they were asked to eat a meal alone. The following week they had to eat
while listening to a description of the food’s tastes and textures. The
third week they were asked to eat while listening to a detective story.
And the fourth week they were asked to eat the meal with three other
women. The meal was exactly the same each visit. The women ate the same
amount at every meal except when they had to listen to the detective
story. On that occasion, they ate an average of seventy-two calories
more—even though they rated their levels of hunger exactly the same on
all four occasions.
Listening to the detective story was the only
situation in which the women’s attention was directed away from their
food. In the first instance, there was nothing else but the food to
attend to; in the second, they were directed to focus on the sensual
qualities of the food. When dining in company, they would have watched
the other women and might have felt like they were being watched,
possibly making them more self-conscious of what they were eating. The
lesson: when we don’t pay close attention to the food on our plates, it
is easy to eat too much.
Memory and Eating
Although
distractions can lead to overeating, the limits of our memory also
contribute to eating too much. When amnesiacs with no short-term
memories were offered meals in quick succession, even just one minute
apart, they kept on eating and consumed full plates each time.
Afterward, they reported no change in their feelings of hunger because
they didn’t remember that they had already eaten.
In studies to
test how important memory is for people without amnesia, British
researcher Suzanne Higgs found that when subjects were prompted to
remember their last meal, they ate less. She discovered this by having
participants come to her lab for lunch at 12:30 p.m. and then again at 3
p.m. for a biscuit taste test. For lunch, participants were given pizza
and asked to rate it as well as their own feelings of hunger and
fullness. In the afternoon, they were again asked to rate their hunger,
fullness, and desire to eat. Half the group was then asked to think
about the pizza they had for lunch and write down their thoughts about
it, while the other half was simply asked to write down whatever
thoughts they wanted. Afterward, both groups were presented with three
plates full of different types of biscuits and asked to taste and rate
them. After eating, the researchers measured how full the participants
felt and how much they ate.
The group that did not write about the
lunch ate more of the biscuits but rated their fullness, hunger, and
desire to eat the same as the other group. Yet the other group consumed
21 percent less of the biscuits.
Dieting also requires a good
memory because it demands that people keep track of how much they eat.
But most people don’t do this very well, and there are multiple reasons
why. Even if we have a good memory, if we eat while multitasking, it’s
possible we won’t remember that we ate at all. Another common barrier to
keeping track of our food is that we may not know what’s in the food or
how much we are eating, especially if we aren’t the ones preparing and
serving it. And if people can’t tell how much they are eating, it’s no
surprise that researchers also have considerable difficulty in measuring
what and how much people eat.
Until now, there has been no
objective way to measure what people eat other than to keep them locked
up in a laboratory, measuring all the food they are served and
subtracting what they leave on their plates. Outside the laboratory,
when people have unlimited choices, they eat different foods in varying
amounts at different times. Therefore, what a person reports eating over
the course of a single day may not reflect what he or she eats over a
week, a month, or a year.
Not only do researchers measuring diet
have to overcome the challenge of variability; they also have to
overcome inherent limitations in memory and attention. How accurately
can people remember what and how much they ate over time?
To help
figure out the best way to measure what and how much people eat,
scientists have to be able to verify whether people are really eating
what they say they are. One method to verify people’s food consumption
is to draw their blood and collect samples of their urine to test the
concentration of various nutrients. If people really ate what they say
they did, we should be able to see some of the food by-products or
nutrients that were absorbed. These nutrients are called biomarkers.
In
one of these investigations, the Observing Protein and Energy Nutrition
(OPEN) Study, funded by the National Cancer Institute, researchers
assessed how well people could remember and report what they usually
eat. Almost five hundred participants were asked to fill out a food
frequency questionnaire detailing exactly how often they ate a serving
of each of the foods listed. Based on their responses, researchers
calculated the average daily calories consumed. Beyond this
questionnaire, study participants were also asked to recall what they
had eaten in the previous twenty-four hours. Their reported consumption
on both the food frequency questionnaire and the twenty-four-hour recall
was checked against blood and urine biomarkers, which indicated the
amount of protein and calories actually consumed.
Compared to what
the biomarkers showed, the food frequency questionnaire suggested that
both men and women underreported what they ate by more than 30 percent.
This enormous calorie gap is, in part, due to the inability of the food
frequency questionnaire to accurately reflect what is eaten.
Nevertheless, even when reporting the foods they ate in the last
twenty-four hours, which depends on short-term memory, participants
still underestimated the quantity of food eaten by up to 20 percent.
Given that, on average, women consumed 2,277 calories per day, their
underestimates ranged from 358 calories at best to 872 calories at
worst. The range of men’s underestimates was even wider: from 337
calories on the twenty-four-hour recall to 1,031 on the food frequency
questionnaire. These “missing” calories could easily represent an entire
meal. In general, overweight individuals tended to underreport more
than those of normal weight. This is probably part of the reason they
are more likely to be overweight in the first place: if they cannot
recognize that they are consuming too much, they cannot easily limit
their intake.
Excerpted from: “A Big Fat Crisis: The Hidden Forces Behind the Obesity Epidemic—and How We Can End It” by Deborah A. Cohen. Excerpted by arrangement with Nation Books. Copyright 2013.
(Credit: Picsfive via Shutterstock)
No comments:
Post a Comment
Please leave a comment-- or suggestions, particularly of topics and places you'd like to see covered