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Video: Is fasting safe?

By “Today” nutrition and diet editor
TODAY
updated 12/19/2006 12:19:52 PM ET 2006-12-19T17:19:52

Want to drop those extra pounds in time for that holiday party? Fast. At least, that’s what some Americans are doing in order to lose weight quickly. A recent article in The New York Times, “I Heard It Through the Diet Grapevine,” explored how some people fast in order to lose weight and detox their bodies, a practice called the “master cleanse.” But does it work? And more importantly, is it safe?

What is fasting?
Many people fast for a day or so, as part of their religious and spiritual practices. Some fast to “cleanse” their bodies, and others fast as a way to lose weight – quickly. Fasting to lose weight can be a hazard to your health. There are various types of fasts. Here are a few:

  • Water: This involves water, but no food. Many patients are instructed to do this, up to 24 hours prior to surgery, in order to keep their digestive tracts clear, so there won’t be complications when they’re under anesthesia.
  • Fruit juice: These have been very popular. They usually focus on organic fruit juices. But people can also include vegetables — either  raw or cooked in soups. Either way, they’re consuming few calories.

The “master cleanse” mentioned in the Times article basically entails a water fast with a little bit of sugar (maple syrup) thrown in to give a slight energy boost. Dieters are supposed to adhere to this fast for a minimum of 10 days. Every day, they drink six to 12 cups of this sweetened concoction for total calories somewhere between 650 and 1,300 per day.

The ingredients are:

  • 2 tablespoons of lemon juice (8 calories)
  • 2 tablespoons maple syrup (100 calories)
  • pinch of cayenne pepper (0 cal)
  • 1 cup water (0 cal)

Is fasting healthy?
While fasting for several days (assuming your fluid intake is sufficient) is not harmful, there’s no evidence supporting its benefits. However, fasts lasting for more than a week, even with some minimal amount of calories, can damage your health. You need to consume protein for body’s needs. If you don’t have eat protein, your body starts to break down your muscle (which is protein) in order to get the necessary amino acids (the building blocks of protein). A long-lasting fast can damage your heart, which is a muscle, as well as your liver and kidneys, which can decrease in size, if you don’t ingest enough protein. Insufficient protein will also impair their functions.

Does fasting cleanse the body?
There is no scientific evidence that fasting detoxes the body. Our bodies are already pretty self-sufficient. The liver is the body’s natural detox center. Other organs, including the lungs, the kidneys, and the skin, also remove impurities and toxins from the body. A fast may give the perception of “cleaning out” your body’s impurities, but that’s not what happens. While some people reportedly feel great after fasting, others feel sluggish, tired, achy, and unfocused. That’s because they’re often not getting sufficient calories. (It’s important to note that these kinds of fasts involve drinking a lot of water and ingesting some salt in order to support the body’s normal salt and water balance.)

Often people who are trying to “cleanse” their bodies, will also use colonics, or enemas. These can be risky to your health, because they can alter your body’s overall salt and water balance. This is also true for herbal tea laxatives.

If you don’t eat and you drink a lot of water, you will urinate frequently. And if you eat few carbohydrates, you’ll also further increase water loss. But this won’t help you lose weight. You’re only depleting your body of fluids, which may make it seem like you’re actually losing weight. Of course, if you eat few calories, you will lose weight quickly, but that doesn’t mean you will keep it off. As the saying goes: easy off; easy on.

Dr. Madelyn Fernstrom’s Bottom Line: If you consume fewer calories, you will lose weight. But fasting to lose weight quickly can put metabolic stress on your body. After fasting for a few days, you risk damaging your body. Losing muscle mass is very unhealthy. Plus, any weight you lose quickly, you will put back on just as easily.

Madelyn Fernstrom, Ph.D., CNS,is the founder and director of the University of Pittsburgh Medical Center’s Weight Management Center. An associate professor of psychiatry, epidemiology, and surgery at the University of Pittsburgh School of Medicine, Fernstrom is also a board-certified nutrition specialist from theAmerican College of Nutrition.

PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.

© 2013 MSNBC Interactive.  Reprints

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