Under normal circumstances you can rely on your appetite to ensure that
you don't overeat. But modern life is not normal circumstances.
Appetite 101
Appetite
is important. It is your body’s built-in mechanism for food intake
regulation. Its job is to drive you to eat enough to meet your body’s
energy and micronutrient needs, and no more. The appetite mechanism
works very well under normal circumstances. Obviously, it never would
have survived millions of years of evolutionary testing if it did not
work to the benefit of our health. But our modern lifestyle does not
constitute “normal circumstances” in relation to the environment in
which most of our evolution took place. Consequently, our appetite
cannot be entirely relied upon to ensure that we don’t overeat.
In
recent years scientists have learned a lot about how the appetite
mechanism works. Let’s take a look at five factors that are now known
to influence appetite and how you can manipulate them to make your
appetite more reliable.
Food in the stomach
Most
people know intuitively that feelings of fullness are generated from
the stomach. When you eat, your stomach distends, or stretches. The
distension of your stomach activates the appetite control switch in the
hypothalamus of the brain, which tells you to stop eating and
diminishes hunger until it is time to eat again. This is how your
appetite switch is turned off. When food enters your stomach it
stimulates the release of a protein called cholecystokinin, or
CCK. When CCK is released, the first thing it does is to close down the
valve from the stomach into the GI tract. This slows the movement of
food from the stomach. The longer food stays in your stomach, the more
full you feel. Because of its effects, CCK is sometimes referred to as
the “feel-full” protein.
The
unique properties of CCK were discovered almost 40 years ago when
researchers at Cornell and Columbia universities demonstrated that
injecting CCK into humans reduced appetite up to 20%.
The
appetite control switch was designed to work best with the natural
foods that humans ate exclusively thousands of years ago. Many of the
processed foods we eat today are far more calorically dense than those
natural foods, meaning they contain more calories in less
space. Unfortunately, these processed foods enable us to eat more
calories than our bodies need before the appetite control switch gets
activated. It is not unusual for an individual to eat a fast food meal
of 1,000 calories in less than 10 minutes. But it takes more than 10
minutes for food to stimulate enough CCK to make you stop eating. Thus,
when you eat high-calorie processed foods, you can easily overeat
before CCK--your body’s natural gastric pacemaker--begins to work and
you feel full.
Your
appetite mechanism will work better if you base your diet in foods with
lower energy density: namely, fruits, vegetables, lean meats and whole
grains.
Blood glucose level
Due
to the recent popularity of low-carb and glycemic index diets, the
average person believes that declining blood glucose levels are the
primary cause of hunger. There is actually little evidence of a causal
relationship between declining blood glucose levels and
hunger. However, there is solid evidence of a correlation between
declining blood glucose levels and hunger. That is, people do tend to
become hungry at the same time their blood glucose level is
decreasing. Whether hunger results directly from the sensing of
declining blood glucose levels by “glycostat” neurons in the brain or
through some intermediary factor remains to be
discovered. Interestingly, the feeling of fullness that occurs
immediately after eating precedes the rise in blood glucose that
follows carbohydrate absorption.
Research
has shown that low-carb and low GI diets do not reduce hunger compared
to other weight-loss diets. It seems pointless to try to regulate your
appetite by eating for blood glucose control.
Leptin production
Leptin
is an appetite-regulating hormone that is produced by fat cells. It
acts on the hypothalamus, the brain’s hunger center, to turn off the
hunger switch. The more fat your fat cells contain, the more leptin
they produce and the more your appetite shrinks.
At
least that’s how it works under normal circumstances. However, there
appears to be a second factor that affects leptin production, and
that’s habitual eating patterns. If you consistently overeat, your fat
cells will reduce their leptin output to accommodate your preferred
eating patterns by allowing your appetite to remain large despite the
fact that you’re getting fatter.
Fortunately,
this effect is reversible. If you restrain your eating for a week or so
your leptin production will return to normal. However, as you lose body
fat, your leptin production will decrease and your appetite will again
increase. It’s a Catch-22! Your best way out is to exercise plenty, so
you can eat as much as your appetite demands without getting fat.
Social factors
Over
the past 30 years, the number of calories in the average American’s
diet has increased significantly. This increase is widely believed to
have been driven by increases in portion sizes in restaurant menu items
and packaged foods that resulted from substantial decreases in the cost
of producing food and competition among food businesses. The
combination of this influence and that of the constant deluge of
commercial advertising for food has essentially inflated our
appetites—or created a breach between our physical and social appetites
for food. Researchers such as consumer psychologist Brian Wansink of
Cornell University have shown that the amount of food we consume is
strongly influenced by the accessibility of food, how much food is put
in front of us, and social pressure to eat more, including the pressure
of commercial advertising. A perfect example of the latter influence is
Taco Bell’s invention of “fourth meal,” a late night meal of fast food
that the television viewer is encouraged to ad to his or her daily
eating routine.
To
reduce the effects of food overabundance on your eating, experts
generally recommend that individuals train themselves to pay better
attention to the physical signs of appetite, hunger and fullness. The
goal is to eat only when physically hungry and, when eating, to eat
only until comfortably satisfied, never stuffed. As you get a better
sense of how much food you really need to satisfy your physical
appetite, you can also train yourself to purchase, prepare, serve and
order smaller portions that meet this standard without exceeding it.
Activity level
Evolution
gave us bodies that are able to store energy reserves for times of
scarcity in the form of excess body fat. These reserves accumulate
automatically when we increase our eating without increasing our
activity level, or decrease our activity level without decreasing our
eating, or simultaneously increase our eating and decrease our activity
level. We modern humans are much less active than our ancestors
were. Evolutionary biologists estimate that our Paleolithic ancestors
each burned 1,000 calories per day more than we do through
activity. But our appetites are the same, which means that the modern
lifestyle tends to make us fat. In such an environment you can’t trust
your appetite, because your body “thinks” you’re trying to store excess
body fat by moving so little.
Everything
changes when you start exercising, however. As you burn 500 or more
extra calories each day through training, your appetite automatically
adjusts to help your body run better—specifically, it increases enough
to replenish the critical fuel stores (mainly muscle and liver
glycogen) that you deplete each day but not enough to prevent the
shedding of excess body fat, which of course slows you down. Research
has shown that when they increase their training load (hence the number
of calories they burn each day), athletes on “ad libitum” diets
(meaning they eat according to their appetite, not by counting
calories) automatically increase their calorie consumption and lose
body fat. Thus, the best way to consistently eat the right amount is to
continue eating according to your appetite and increase your training
in pursuit of performance.
Nutrition article courtesy of PacificHealth Laboratories, makers of nutrition tools such as Accelerade, Accel Gel, Endurox R4, Endurox Excel and much more. For product information or to purchase products, please visit www.pacifichealthlabs.com.
