Getting the Skinny on Fasting
Adapted From: Weight Loss Kit For Dummies
When you choose to go without food,
you call your behavior fasting. When a catastrophe such as war or famine
keeps you from getting food, that's called starvation. Politically and
socially, fasting and starvation are very different phenomena, one voluntary,
one not. But to your body, no food means no food. Period. Sensing danger, you
involuntary set off all kinds of internal alarms as basic metabolic defenses
spring into action. The resulting physiological brouhaha may have distinctly
unpleasant consequences.
Your body uses 79
percent of the energy (calories) you consume each day to run its organs and
systems: your heart, your lungs, your digestive tract, and last, but definitely
not least, your brain.
Your body runs on glucose, the
product of metabolism. The foods most easily metabolized to glucose are
carbohydrate foods, the plant foods such as fruits, veggies, and grains. Fat
foods are second choice, a less efficient but still useful source of glucose.
Under normal circumstances, there is no third choice. Except in emergencies,
you use protein foods only to build and repair body tissues, not as a source of
energy.
You can store carbohydrates as
glycogen, which is easy to change to glucose. You can store fat as, well, fat.
When it's crunch time — you're stuck on an ice floe in the Arctic with no
supply ship in site — the fat breaks down into fatty acids from which your body
extracts small amounts of glycerol (a fatty substance), which yields
little bits of glucose. Therefore, if you miss a couple of meals, you can get
by for a day or so on your carb and fat reserves.
Without adequate
supply of carbs, your body looks for a new glucose mine, and what it finds is
the protein in your muscles and organs. To compensate for the lack of protein,
your body will literally begin to digest itself, breaking the proteins in
muscle and organ tissue into amino acids, which yield pyruvate, a
compound that can be used to manufacture glucose. Well, that sounds good. But
it's not.
You can store carbs, and you
can store fat, but you can't store protein. You need a new supply every day.
Without it, you cannot make the red blood cells you need to carry oxygen to
every tissue. You cannot make enough new cells to compensate for your natural
daily loss of muscle tissue or the natural daily loss of cells lining your
digestive tract. And without sufficient protein, you won't have enough albumin,
a protein in blood that helps maintain fluid balance (the amount of liquid
inside and outside each cell).
As a result
Another problem with using protein
for energy is that to process the protein your body needs lots of water. As a
result, while you lose weight, most of the weight you lose is liquids your body
needs for essential functions, like breathing, and digesting, and . . . well,
all that good stuff.
Like protein depletion, water
depletion (dehydration) has serious consequences. Feeling thirsty is a signal
that you've lost an amount of liquid equal to about 1 percent of your body
weight. When that doubles to 2 percent, your circulation slows for lack of
water in blood cells and blood plasma (the liquid around the cells inside the
blood vessels).
If your water loss doubles
again, to 4 percent of your body weight (5 pounds for a 130-pound woman; 7
pounds for a 170-pound man), your have less water in your body tissues so you:
When your water
loss equals 10 percent of your body weight, you're dizzy, with muscle spasms, on
the verge of kidney failure. At 20 percent, it's good-bye, Charlie.
If this list of problems isn't
enough to make you swear off fasting until your start to nibble at your own
muscles, consider this: When your body turns to your muscles and organs for energy,
it eventually runs into a wall. You have only so much protein tissue available.
In the end, it will be used up, your heart will stop, your brain will shut
down, and you will die of starvation — if dehydration doesn't get you first.
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