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. |
How your body responds to fasting
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
- You feel weak (not enough oxygen).
- Your muscles thin down (not enough new cells).
- Your digestion is botched up (ditto).
- Your belly swells (too much fluid retained).
- You are light-headed (not enough liquid to keep blood flowing to the brain).
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:
- Feel sick to your stomach.
| 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.
Medically sanctioned fasting
Believe it or not, a few situations warrant going without food can be good medicine. The key is the phrase "medically supervised." Patients fasting in a hospital under a doctor's care don't just stop eating. They get specially prepared products sold only to doctors and hospitals that contain sufficient amounts of glucose and protein to protect vital muscles and organs. These products also contain nutrients such as vitamins and minerals to prevent deficiency disease.
Medically supervised fasting is meant only as a short-term program for people who meet very specific criteria:
- They are more than 100 pounds overweight.
- They have a BMI (body mass index) higher than 30.
- They have a BMI 27 to 30, but also have weight-related health problems such as diabetes or high blood pressure.
Neither fasting nor very low calorie diets are recommended for:
- Women who are pregnant or breast-feeding.
- People who have medical conditions or are using medication that make it difficult to tolerate the side effects of severe calorie cutting.
| Supervised fasting is a short-term option that must be carefully monitored to prevent serious health risks such as heart failure. Although fasting can jump-start a weight loss program, experts value it for its long-term weight control. In other words, as they say on those daredevil TV car commercials, don't attempt this one at home. |
|
