Depending on your body weight, you can survive anywhere from 28 to 73 days without food, reports Scientific American. Fasting has been practiced for thousands of years in Christianity, Judasim and Eastern religions as a way to commune with God and purify the soul. Today, some people still fast for spiritual reasons, but many fast to detoxify their body or to lose weight.
Benefits
Modern practitioners, such as Elson Haas, M.D., and early modern fasting proponent, Herbert Shelton, N.D., believe that fasting rids the body of toxins and rests the digestive system. Advocates say that fasting can improve a variety of conditions, including allergies, heart disease, atherosclerosis, diabetes, hypertension and cancer. Health researcher Benjamin Horne says, in the December 2007 "U.S. News & World Report," that fasting resets your body's sensitivity to insulin and glucose, which enhances your metabolism and assists with weight control. Notably, however, most experts advise fasting to detoxify your body and enhance your health and not for weight loss per se.
Energy Balance
Every moment of every day, whether you're sleeping or awake, your body burns energy doing body maintenance activities. The brain uses some 20 percent of the energy you consume, even at night while you sleep, masterminding your body's operations. Other organs, such as the heart, and lungs work non-stop, and you are constantly repairing and replacing cells and tissues. You eat food to provide the energy every cell, tissue and organ needs to keep operating. When you don't eat food, your body turns to other sources for energy, including fat and protein. Fasting proponents Elson Haas and Leon Chaitow believe that detoxification occurs during fasting because once your body has depleted carbohydrates in your blood, liver and muscle, it relies on fat for fuel, and so it burns fat cells where toxins presumably reside.
Fast Weight Loss
Fasting might help you lose weight, at least temporarily. Certainly, you lose weight while you fast. How much weight you lose depends on how much you weigh and how many calories you burn off in activity. For every 3,500 calories you eliminate by not eating or by exercising you lose 1 lb. of weight. A 240 lb. 30-year-old man with a sedentary lifestyle burns around 2,400 calories per day. Over seven days, he creates a calorie deficit of 16,800 calories and would potentially lose about 4.8 lbs.
Cautions
Many medical experts question the usefulness of fasting, especially for weight loss. There is little scientific evidence that documents the detoxification effects of fasting. Also, fasting triggers starvation mode in your body, so your metabolism slows and you burn fewer calories. Further, once you stop fasting, you will regain weight if you don't alter the lifestyle choices that lead to your extra weight in the first place. Finally, the effectiveness and long-term mechanisms of fasting to induce weight loss in humans has not been widely studied. Researcher Benjamin Horne notes that most research has been done on roundworms, rodents and slugs. Consult your doctor before undertaking any fast.
References
- Calculators-free.com: Demonstration Calculator
- FalconBlanco.com: Fasting; Herbert Shelton
- Health.net; Fasting, Mono-Diets and Raw Food Days; Leon Chaitow
- Health.net; Nutritional Program for Fasting; Elson Haas
- MayoClinic.com; Do Detox Diets Offer Any Health Benefits?; April, 2010
- "Scientific American"; How Long Can a Person Survive Without Food?; November 2004
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