Preventing Childhood Obesity - Evidence Policy and Practice.pdf

Evidence on the food environment and obesity
opposed to only 2% for white audiences. 24 Given that
studies indicate that exposure to food advertisements
influence food preferences, this level of exposure
could explain, in part, the health disparities seen
among racial and ethnic minorities. 25
Automatic responses to
the food environment
Understanding the way in which humans respond to
environmental stimuli is critical to identifying how
the dramatic changes in the food environment have
been able to transform the eating behavior of
Americans, and is now quickly influencing people
across the entire globe. People are hardwired to
respond automatically to food and images of food.
These responses are immediate and the physiological
reflexive responses are largely uncontrollable. For
example, when people are exposed to images of appetizing
food, their brains automatically and reflexively
secrete dopamine, activating at least five separate
reward centers in the brain. 26 This activation leads
to food cravings. The physiological pathway involving
dopamine excretion in response to food images
involves the same neural pathways that are associated
with drug addictions. 27 The magnitude of
the arousal of the reward centers varies considerably
across individuals and is believed to explain the
variability of drives for food, hyperphagia and
obesity. 26 Given that food advertising and food availability
have mushroomed, people are being artificially
stimulated throughout the day to feel hungry and
crave food.
Limited ability to exercise control
Not only are people unable to prevent the automatic,
reflexive responses to food images and foods (including
salivation), but it may be difficult for many people
to distinguish between artificially induced hunger
and desire for food and true hunger that comes from
a low blood sugar. Moreover, people may be unable
to recognize that they are being artificially stimulated
to feel hungry, since many of the cues are imperceptible.
28 Humans have the ability to perceive images
through visual systems that are not perceived by
the part of the brain that provides conscious
awareness. 29,30 Although this type of stimulation
may occur during a small proportion of the time,
it does not require much for individuals to be out
of energy balance. Large amounts of calories are
available in small volumes of food; a small candy bar
has over 200 calories. Relatively small amounts of
calorie excess are believed to be fueling the obesity
epidemic.31
Evidence that people can be stimulated to eat too
much without their awareness or insight comes from
a variety of studies. In one study, subjects exposed to
subliminal images that were unrelated to food, were
influenced to drink a greater quantity of an energy
drink, and rate it more favorably. They had no subjective
awareness that their behavior was affected in the
least. 29
Another study that showed people lacking insight
into the quantity of food consumed was demonstrated
when subjects were provided with soup in self - refilling
bowls. Without cues that let people judge quantity,
subjects ate 73% more than the participants given
soup in normal bowls, yet did not feel more satiated. 32
People also have a limited capacity to judge volume
and portion sizes. In several studies, individuals
were unable to correctly judge the volume held by
two glasses of different shapes and incorrectly thought
that a tall narrow glass held more liquid than a
short wide glass. 33,34 Since people do not have
any internal signals that allow then to regulate the
quantity of food to eat, 3,35 they rely on external
cues, such as portion sizes, to determine how much to
consume.
People usually consume more calories than they
need to when offered too many, and they do not compensate
for the excess by eating less at subsequent
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meals. 39 Instead, excess calorie consumption initiates
the pathway to store excess energy as fat. People
cannot easily judge when this happens.
Studies in the field of behavioral economics indicate
that individual choices are strongly influenced
by the means through which the choices are presented.40
People exercise a limited amount of cognitive
decision making, and typically rely on specific
heuristics to make decisions, particularly when they
are overwhelmed by too much information or are
under stress. In these cases, people rely on default,
impulsive reactions, rather than considered cognitive
decision making. 41,42 Heuristics governing food
choices have more to do with factors such as price,
convenience and emotional associations rather than
concerns about health.
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