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Is Fasting Healthy?

Fasting has been practiced for centuries. But can it really help you lose weight and get healthier?
By Susan Seliger
WebMD Feature

It sounds so simple -  no choices, no counting calories, no cooking. Just say 'no' to food, and start fasting for quick weight loss and other health benefits.

After all, Beyonce did it. She said she lost 20 pounds by fasting (and using a concoction of syrup, lemon juice, water and cayenne pepper) for her role in Dreamgirls.

But what about the rest of us mortals? We wonder:

  • Is fasting an effective way to lose weight?
  • Can fasting really help with medical conditions such as heart disease, high blood pressure, asthma, arthritis and other auto-immune disorders?
  • Will fasting help you live longer?

And finally, is fasting healthy? Although fasting has been practiced for thousands of years, the question is still a subject of intense medical debate. WebMD consulted experts on weight loss and fasting for some answers.

Fasting and Weight Loss

If you weed through all the controversy, you'll find that most medical experts agree on one thing: fasting is not a healthy weight loss tool.

"The appeal is that [fasting] is quick, but it is quick fluid loss, not substantial weight loss," says Madelyn Fernstrom, PhD, CNS, founder and director of the University of Pittsburgh Medical Center's Weight Loss Management Center.

"If it's easy off, it will come back quickly" -- as soon as you start eating normally again, she says.

Even some proponents of fasting for other medical purposes do not support fasting for weight loss. Some say it can actually make weight problems worse.

"Fasting is not a weight loss tool. Fasting slows your metabolic rate down so your diet from before the fast is even more fattening after you fast," says Joel Fuhrman MD, author of Eat to Live: The Revolutionary Plan for Fast and Sustained Weight Loss and Fasting and Eating for Health.

Fasting for weight loss carries other health risks as well.

While fasting for a day or two is rarely a problem if you are healthy, "it can be quite dangerous if you are not already eating a healthy diet, or if you've got liver or kidney problems, any kind of compromised immune system functioning, or are on medication -- even Tylenol," says Fuhrman, a family physician in Flemington, N.J..

Even worse for dieters is that fasting for weight loss "distracts people from the real message of how to lose weight: lower fat intake, eat five fruits and vegetables a day, drink water and stop drinking other liquids, walk 30 minutes a day, and get more sleep," says Fernstrom, an associate professor of psychiatry, epidemiology, and surgery at the University of Pittsburgh School of Medicine.

In addition, other practices that are often combined with fasting for weight loss, such as colon cleansing, carry their own risks.

"Fasts are sometimes accompanied with enemas to cleanse your intestinal tract, and that can be very dangerous," says Fernstrom. "The intestinal tract has a lot of good bacteria. When you are changing that balance, the good bacteria are affected, too."

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