Why Do You Continue to Eat When You're Full?

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The premise that hunger makes food look more appealing is a widely
held belief.

Prior research
studies have suggested that the hunger hormone ghrelin, which your
body produces when it’s hungry, might act in your brain to trigger
this behavior.

New studies
suggest that ghrelin might also work in your brain to make you keep
eating "pleasurable" foods when you’re already full.

Scientists
previously have linked increased levels of ghrelin to intensifying
the rewarding or pleasurable feelings that can be obtained from
cocaine or alcohol. Researchers observed how long mice would continue
to poke their noses into a hole in order to receive a pellet of
high-fat food. Animals that didn’t receive ghrelin gave up much
sooner than the ones that did receive ghrelin.

Humans and
mice share the same type of brain-cell connections and hormones,
as well as similar architectures in the "pleasure centers"
of the brain.

Sources:

Dr. Mercola’s
Comments:

Isn’t
this really the million-dollar question? Why do people continue
to eat, even after their stomachs are full or even stuffed? If there
was a simple answer, I’d gladly share it with you, but the
reality is that people overeat for a variety of reasons – and
many of them are rather complex.

As this new
study suggests, one of the forces driving you to eat a second helping
or an extra dessert even though you’re full is the hormone
ghrelin. Ghrelin (pronounced GRELL-in) is produced mainly by your
stomach, although it is also made in other organs, such as your
intestines and your kidneys.

Ghrelin has
been dubbed the “hunger hormone” because in previous studies
people given the hormone became so ravenous, they ate markedly more
than their usual food intake. Ghrelin, it appears, may also act
on your brain’s “pleasure centers,” driving you to
reach for another slice of cheesecake simply because you remember
how good the first one tasted and made you feel (at least in that
moment).

What Influences
Your Body’s Level of the Hunger Hormone?

Your body’s
level of ghrelin can be influenced by many factors, including your
lifestyle habits. For instance, chronic lack of sleep increases
ghrelin, making you feel hungry when you don’t really need
to eat. This is likely one reason why a lack
of sleep can make you gain weight.

Insulin
may also play a role
in regulating ghrelin levels. In one study,
ghrelin levels were monitored in eight non-diabetic adults as they
were given a two-hour infusion of insulin. Shortly after the infusion
began, levels of ghrelin began to drop. When the insulin infusion
was stopped, levels of the hunger hormone began to rise and rapidly
returned to normal.

Since insulin
is already known to increase levels of leptin – the "obesity
hormone" that tells your brain to curb your appetite after
eating – the findings suggest that insulin plays an important
role in controlling what you eat.

In other words,
let’s say you eat a sugary dessert. Your production of insulin
increases so that the sugar in your blood can be taken to cells
and used for energy. Eating this sugar also increases production
of leptin, which regulates your appetite and fat storage, and decreases
production of ghrelin, which helps regulate your food intake. The
idea is that when you eat, your body knows it should feel less hungry.

But there
is another major key here that is often overlooked, and that is
when you eat certain foods, namely those that contain fructose,
this important cycle does not occur.

Is Fructose
Driving You to Overeat?

Fructose, a
cheap form of sugar used in thousands of food products and soft
drinks, can damage human metabolism and is likely fueling the obesity
crisis. This is because your body metabolizes
fructose in a much different way
than glucose, and fructose
is now being consumed in enormous quantities, which has made the
negative effects much more profound.

If anyone
tries to tell you “sugar is sugar,” they are way behind
the times. It is increasingly becoming clear that just by eating
fructose, including high-fructose corn syrup, you may be drastically
increasing your tendency to overeat.

You see, glucose
suppresses the hunger hormone ghrelin and stimulates leptin, which
suppresses your appetite. Fructose, however, has no effect on ghrelin
and interferes with your brain’s communication with leptin,
resulting in overeating.

This is why
fructose may contribute to weight gain, increased belly fat, insulin
resistance and metabolic syndrome – not to mention the long
list of chronic diseases that are related to these conditions.

Are There
Other Factors That Come Into the Mix?

Yes, ghrelin,
leptin and insulin responses in your body may be major players in
your ability to regulate your food intake, but they are not the
only ones.

Stress, anger,
sadness and just about any other negative emotion can also lead
you to seek
food as a coping mechanism
and ultimately overeat. And subconscious
cues you pick up from portion sizes, food visibility (such as passing
by a candy dish on a desk) and food proximity (standing near the
food table at a party) can also influence
how much you eat.

Gary Taubes,
who wrote the landmark article What
if it’s All Been a Big Fat Lie?
, also recently offered
a very interesting alternative explanation for why people overeat.
He suggests that people overeat because their fat
tissue is accumulating excess fat
. And why does fat tissue do
this?

Because dietary
carbohydrates, especially fructose, are the primary source of a
substance called glycerol-3-phosphate, which causes fat to become
fixed in fat tissue. At the same time, this diet raises insulin
levels, which prevents fat from being released.

Practical
Tips to Keep Your Eating Under Control

The solution
to normalizing your ghrelin, leptin and insulin levels is fairly
straightforward, and this is to eat a diet that emphasizes good
fats and avoids blood sugar spikes – in short the dietary program
detailed in my
nutrition plan
, which emphasizes healthy fats, lean meats and
fresh vegetables, and restricts sugar and grains.

If you want
to take your health to the next level, I highly recommend finding
out your nutritional
type
as well, and then eating a diet according to your unique
biochemistry.

This, combined
with a regular
exercise program
and a tool
to handle emotional eating
, will be your key to controlling
your motivation to eat.

Related Links:

January
20, 2010

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