Good day and thank
you for attending To Eat or Not to Eat, a discussion on the diversities of why
people desire to eat or not eat. My name
is Rebecca and I will be your counselor for this session. I am here to facilitate healthy discussions
on the physiological factors of hunger and satiety [state of fullness or
satisfaction], and to answer any questions that you may have regarding healthy
eating and eating disorders. During this
time I will be reviewing myths about hunger and satiety, but first, let me
explain some of the physiological factors that cause people to eat or not eat,
and then I will open the floor for questions.
Taste is a major
factor in hunger, a fondness for something sweet, fatty, or salty normally
carries with it a high positive-incentive value causing humans to eat. Acquiring these taste preferences from our
ancestors sweet, fatty foods mean high energy, rich in vitamins and minerals, whereas
salty foods mean sodium enriched, all are vitamins and mineral which the body
needs to stay in optimal health. Most of
us can think of a time when we have had a craving for something. It may be the body’s way of indicating it is
missing needed nutrients. On the other
end of the spectrum, humans have developed what is known as taste
aversions. Normally, foods that carry
with them a bitter taste are associated with toxins or illness and should be
avoided. In essences, learning to eat
healthy, nutritious foods is a learned trait, but caution should be used as
todays manufactures create foods that we crave, but remove the nutrients during
the manufacturing process (Pinel, 2009).
Just as we learn
what to eat from our ancestors, when we eat is another factor passed on through
cultural traditions. Many families
within the United States, for example, eat several full meals each day. Whereas animals eat small meals throughout
the day when food is readily available, when it is not, they adapt to their
conditions. Almost everyone becomes
hungry just before it is time for a normally scheduled meal. Why you ask; this is the body gearing up to
balance the meal about to be consumed.
The body goes into what is called a cephalic phase, preparing to soften the
intake of food, also called the “homeostasis-disturbing influx, by releasing
insulin into the blood and thus reducing blood glucose” (Pinel, 2009, p.
301). This means that hunger is caused
by the anticipation of food, not that our body’s need energy.
Satiety helps to
determine how much is eaten; caused by not only the amount of food, but also
the nutritive density, which was discussed earlier, within the gut and glucose
entering the bloodstream. Repeatedly
eating the same foods, as demonstrated through the studies of sensory-specific
satiety, creates satiety more rapidly than when a variety of foods are
introduced (Pinel, 2009). Serving a
variety of palatable foods, what Pinel (2009) calls a cafeteria diet, leads to
overeating as satiety is taste-specific.
The positive-incentive value of food decreases the more you eat it
causing you to move to other foods if available. This is an important point when you consider
introducing appetizers prior to consuming normal meals. An appetizer effect takes place; small
amounts of food increase the cephalic-phase of the eating process, increasing
instead of decreasing hunger. Additional
studies indicate that satiety may depend on whether we eat alone or with others
(Pinel, 2009). Human females have been
shown to eat less to conform to society’s visions of the acceptable body size,
while yet others may tend to overeat to be sociable.
Before we move to
questions, I want to address a few myths about hunger and satiety. First, early experiments suggested that the
two regions within the hypothalamus [a neural control center in the brain]
controlled satiety and hunger; the ventromedial hypothalamus (VMH) and the
lateral hypothalamus (LH), respectively.
As it turns out, the hypothalamuses main function is to regulate energy
metabolism; studies with bilateral VMH lesions were shown to increase blood
insulin levels which control the production and breakdown of body fat for
different forms of energy use. Bilateral
electrolytic lesions to the LH were shown to produce aphagia, complete
restriction of hunger, and adipsia, complete restriction of thirst; however,
further study also produced a wide range of severe motor disturbances and a
general lack of responsiveness to sensory input. Another myth is with respect to the gastrointestinal
tract. Initially, hunger was thought to
be a product of contractions caused by an empty stomach and satiety the feeling
of a full stomach. Later it was
“discovered that the stomach and other parts of the gastrointestinal tract
release chemical signals to the brain, evidence began to accumulate that these
chemicals were peptides, short chains of amino acids that can function as
hormones and neurotransmitters” (Pinel, 2009, p. 307). As you can see, even though initial
conclusions may prove to be incorrect or only partially correct continued
studies are always advisable and can provide more conclusive results.
Are there any
questions?
Obesity Session:
Lindsey – My
parents were both obese, is that why I am?
Although there are
some indications that an insatiable appetite and the accumulation of body fat has
genetic implications, the majority of obesity today is, more than likely,
caused by our increasing meal sizes. Throughout evolution consuming large amounts
of high-calorie foods was used as a survival technique, excess food was stored
as body fat and used during times of food shortages (Pines, 2009). Although in today’s society this is no longer
needed, as there is an abundance of positive-incentive value food supplies. However, customs and traditions still pass on
the consumption of large meals and eating at social gatherings. This, according to Pinel (2009), unfortunately
perpetuates the increasingly high rates of obesity. Thanks to continued studies on such syndromes
as Prader-Willi syndrome, a genetically caused chromosomal disruption causing
insatiable hunger, researchers are continuing to look at many of the genes that
affect appetite to provide additional answers on hunger and satiety.
Robert – My
girlfriend and I eat together all of the time, so we eat the same food and
amounts of food, but she never gains weight like I do. Why is that?
It appears that
while your energy intake may be the same, each of you is at a different level
of energy output. As the question
reflects, when energy intake exceeds energy output, a noticeable difference in
weight gain will take place. Concerning energy
output, each person has three factors that differ in the degree to which energy
is metabolized, regulated by the hypothalamus.
The basal metabolic rate is the rate at which a resting body utilizes
energy to maintain itself. An adjustment
to the efficiency rate in which the body utilizes increasing levels of body fat
is called diet-induced thermogenesis. Finally,
activities such as fidgeting, posture, and muscle tone are called nonexercise
activity thermogenesis, according to researchers, this adds to dissipating
excess energy (Pinel, 2009). Again, the
answer is each person has a different level to which he or she maintains and expels
stored and excess energy.
Anorexia Session:
Nancy – My mom
says that I became anorexic because I’ve been reading too many Cosmo magazines
and want to look like those girls. Maybe
I did, but I really just don’t crave food.
What do you think it is?
While society
provides extremely slender figures as an example of exuberance and health, this
can become very confusing to a child as he or she experiences a blossoming body
and raging hormones of pubescent’s. With
anorexia the body image is distorted, while a person may be a healthy, normal
weight he or she views him or herself as fat (Pinel, 2009). Thus, beginning and maintaining the obsession
about body image, resulting in life threatening starvation processes to
maintain slenderness. This starvation increases
the positive-incentive value of food; however, individuals who have had little
to eat experience an adverse effect in the consumption of meals. As mentioned previously, the gastrointestinal
tract releases chemicals, called peptides, once released into the bloodstream,
individuals with food deprivation experience extremely noxious effects which induce
a conditioned taste aversion to food, acting as a satiety peptide; decreasing
the appetite.
Tyra – I don’t eat
because every time I do, I just feel sick! Do you know why this is?
Studies show that
particular peptides in the gut, namely cholecystokinin (CKK), induce illness
which creates the conditioned taste aversion, decreasing the appetite; it also
creates nausea in humans (Pinel, 2009). This
may be what is causing you to feel sick.
I want to thank each
of you for attending To Eat or Not to Eat.
It is my hope that you have learned some valuable information about the
diversities of eating and that I have answered all your questions. Please do not hesitate to contact me with
additional questions you might have.
Thank you again, and have a wonderful day.
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