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7 Facts on Fasting

By Pamela Peeke, MD, FACP, MPHMay 27, 2010
From the WebMD Archives

Open up any celebrity mag rag and you’ll read at least one story about an actress or actor who’s used some kind of fast to drop weight quickly and look “amazing.” For people who are desperate to jump start their weight removal, fasting seems appealing. Others might think it’s the way to detox the body from all of the junk food they’ve eaten and get a fresh start on a healthy lifestyle.

So what’s true and what isn’t?

On my WebMD Diet Exchange, kamiebear 19 posted:

“Okay so I have a dilemma. My boyfriend told me about a co-worker who fasted for 9 days straight with nothing to eat or drink beside water and juice. The guy told him he lost 20 pounds in that time and had BMs during the 9 days. He said it was a great way to detox your body and even better before you start a habit-changing diet. I read that sometimes this does absolutely nothing for you and can cause your metabolism to slow down enough to where your body will store fat AFTER the 9 days of fasting. Has anyone out there had a bad experience with fasting? What about a good experience? Help!”

Kamiebear has raised the usual range of questions, so let’s dig in and help her out.

Here are 7 facts on fasting:

1. Fasting has been around forever. It was traditionally used in religious practices as a mode of penitence as well as a golden opportunity for reflection and introspection. It’s also been used by political protesters to gain media exposure and draw attention to their message. Will fasting “detox” you? Heck no! Don’t insult your body. You don’t need to starve yourself to maintain optimal colonic health.

2. There is absolutely no scientific evidence showing that fasting will detox or cleanse your body. However, you can do harm by not stimulating your colon with fiber to help maintain normal motility and thus regularity. And of course, your GI system thrives on healthy nutrients continuously flowing through the lining of the gut.

3. Can fasting help you prolong your lifespan? There is no data on this as yet. How long you fast (once a month, three times a week) is an issue. As well, what kind of fast are we talking about? Scientists have been studying severe caloric restriction for years in animals. You might say they are kept in a state of semi-starvation. Indeed, these animals do have a lower incidence of some medical conditions, but at what price? No one can ask the animals if they’re enjoying any of this. On the other hand, keeping total calories under control with a healthy lifestyle that includes physical activity is a reasonable way to rein in calories and achieve an optimal life span.

4. People seeking weight reduction by fasting have an endless array of ways to do this, from water only, to all of the Hollywood driven formulas (lemon juice, cayenne). You can fast one day or every other day for a period of time, or semi-fast for 12 hours and eat lightly for the rest of the day. The options are endless.

5. Can you actually drop weight and keep it off with fasting? In a word, no. Remember the last time you had the flu and couldn’t keep anything down? Yep, you did drop some weight, most of it water weight, and perhaps a pound or two of fat, depending upon the length of non-eating time. However, as you recovered, you probably also remember in vivid detail how your hunger kicked in big time and before you knew it, you’d compensated for the weight loss and then some. This is actually a beautiful example of how incredible your body is when you provide it with a survival challenge.

6. Please give your body and biology a round of applause. The primal survival mechanisms go into overdrive when you stop eating at a normal level. For all your brain and body knows, you’re stuck on an island with no food. Within a short period of time (much shorter if you’ve fasted or severely restricted your calories before), your baseline metabolism falls to help save your life. The fewer calories you need to live on, the longer you’ll last. Then, when food is finally available, your hunger emerges like a sleeping giant. Most people overcompensate by overeating. Heck, you know this can happen any time, like when you skip a meal or your mid-afternoon snack. At the next meal, you’ll over eat to compensate. People, you’re playing with powerful primal drives that will win every time you challenge them.

7. What happens when you try to fast for a long period of time? Not good things. Your body needs a baseline of electrolytes, minerals and vitamins to survive. You can get by about 48 hours without them and then you start running into trouble. Dehydration, dizziness, fatigue, constipation and cold intolerance are typical, as well as mental grogginess. It’s difficult to achieve restful sleep when you’re hungry, and prolonged fasting can take a toll on moods as well. This is why most religious fasts take place over 24 hours, not 24 days.

Circling back to kamiebear, here are my thoughts on her query. Don’t fast for 9 days. At least half of that was water weight. When you don’t eat carbs, you shed pounds of water, as H2O is used to store carbs in the body tissues. Also, you’ll start to drop muscle which impairs your calorie burning engine – body muscles. Regarding detox, I’ve already made it clear that this is a totally incorrect assumption. And indeed, kamiebear is right when she noted reading that this kind of starvation fasting is not healthy and deleteriously impacts on metabolism. I guarantee you that the young man who fasted for 9 days will soon pack the pounds right back on and then some.

What’s the solution for people eager to see fast results and to jump start their program?

  • First, you need to lay down a strong foundation for calorie burning with your muscles. Hit your weight training. Burn it up with intensity in cardio. Yes, it’s work. What’s an important goal in your life that isn’t? Just keep it enjoyable (dance!) and consistent in your daily life (get it up on the calendar).
  • Next up, nourish with smart and satisfying foods that satisfy. Spread a wedge of Laughing Cow lite cheese on a thick multigrain cracker. That will last you for 2 hours. It’s got high quality fat, protein and carb along with fiber. Love it! Keep it simple, folks. Julia Child does not have to be involved. Have a treat here and there, and just watch the portion size. Share treats when you can. It’s all about having that wonderful taste, not a mountain of the delectable. Veggies, veggies and more veggies with a little fruit will allow your gut to maintain optimal colonic health. You’ll definitely be regular. That’s a natural detox!

Finally, occasional fasts with water and/or juice for religious reasons are fine. For daily living, go for a balance of fabulous nutrition and an active lifestyle. Don’t turn yourself into a science fair project. Mother nature rules! She always wins in the end.

Have you tried fasting to lose weight? Post your comments on the Diet Exchange.

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