Do You Need a “Detox” Fast? Read This Before Forsaking Your Fork!

As a nutritionist, I get questions all the time about the potential benefits of fasting.
People fast for many reasons — for quick weight loss, to “detox” the body, for religous purposes, or even as a political protest. Here is the latest info on the myths and facts of fasting.  Before you forsake your fork, read this:

Fasting and weight loss
Most experts (this one included) do NOT recommend fasting as a way to lose weight.  If you’re itching to shed pounds, a drastic cut in calories may see like the fastest way to see instant results.  However, when you eat less food, your metabolism slows down to conserve energy. Then, when you go back to your usual diet, your lowered metabolism may cause you to store more energy, so you will likely gain back the weight you lost and possibly even put on more weight when eating the same calories you did before the fast.

Fasting to “detoxify” the body
Many fad diets include a “detox” phase during which dieters are instructed to drink only water or herbal teas. But there is scant scientific evidence showing that fasting will detox or cleanse your body. Fasting does not boost the body’s disposal system, or cleanse your body in a healthy way. Some people say they feel great during or after a fast. They might feel great because they believe fasting is healthy or has a significant spiritual meaning, or they might feel great because severe calorie restriction (like fasting) can produce feelings of happiness or even euphoria. In either case, fasting isn’t actually doing a body good. What’s the long-term solution for cleansing your body, then? Eating a sensible diet with plenty of fruits, vegetables, whole grains, lean protein, and unsaturated fats.

However there are some interesting studies indicating that, under some circumstances (and always under medical supervision) fasting may boost health.
NOTE: If you are considering any type of fast, it is imperative that you check with your doctor first. Fasting can be harmful for some people, including pregnant and breastfeeding women, the elderly, and individuals with certain health conditions.

Fasting and heart health
News emerged this week that regular fasting may be good for your heart.  A study found that periodic fasting not only decreases the risk of heart problems and diabetes, but may also lower blood sugar levels. The researchers found that people who fasted regularly had a 58 percent lower risk of coronary disease compared with those who said they didn’t fast.  The study was conducted by researchers at the Intermountain Medical Center Heart Institute (IMCHI) in Utah. Study findings were presented at the ongoing annual scientific sessions of the American College of Cardiology in New Orleans. While these findings are intriguing, experts say it is still too early to conclude that fasting should be used as part of a heart health prevention plan.

Fasting for a longer life
Meanwhile, caloric restriction, while not a strict fast, has been shown in numerous studies to extend life in rodents, yeast and various insects. The National Institute on Aging funds several projects investigating this possibility in monkeys. Investigators at Washington University in St. Louis are studying members of the nonprofit Calorie Restriction Society, a group that exists to promote this type of research in humans. Several compounds also are under investigation in hopes of reproducing the benefits without the negative aspects and challenges of ingesting so little food.

The Bottom Line: For most healthy people, a day of fasting for spiritual or religous purposes will not cause harm.  However, while there is some interesting research on the benefits of fasting/calorie restriction, more studies are needed to determine just how fasting can effect the body.  So hold on to your fork and keep eating healthy meals and snacks.  It’s good for your body… and tastes good too!

— Katherine


  1. Jessica says

    Hi, I’m a dietitian and I get asked a lot about fasting from friends at church (it’s non-denominational with baptist overtones) and people I know who are missionaries. Jesus fasted for 40 days/nights while he was alone praying. I’ve known several people who have done this, following his example. The only thing they take in during that kind of fast is water, maybe juice, and broth. I also have a friend who recently did a 7-day water fast (he was moved to do it in order to pray for a specific situation that needed God’s intervention). I’ve fasted for 24hrs before when there was something I really wanted to pray about and the answer could only come from God. But it’s hard! 40 days/nights I could never do, nor the 7-day water fast, but I want to respond with sensitivity to people who feel led to do that. It’s so hard as a RD though! I’m trying to reconcile my faith with my RD background. Any thoughts?

  2. Beth M. says

    On a religious note, I believe and fully support fasting as a form of spiritual discipline. It’s a way to “humble the flesh” and bring someone closer to God. However, it’s never recommended for children or those who are pregnant or sick.

    On the other hand, as part of your diet, I agree with Katherine. Fasting should never be done to lose weight and I believe there are other ways to detox. I think a lot of people feel great when they go on a fast because for the first time they’re really in tune with their body. I’ve been practicing on focusing more on my body and the signals it gives me. I focus on how I breath; I wait for the actual feeling of hunger until I eat (not starving, just right when I know I’m oficially hungry and water doesn’t subdue the hunger pains); and I even focus on how I move, trying to always keep my body strong and in balance. I’ve gone through a 24 hour fast and it is tough. It left me weak and once I got to eat the next day, I overindulged which I believed put my digestive system in shock. I’d rather eat healthy, workout and if necessary, detox with raw foods before I fast. Plus fasting puts me in a seriosuly bad mood which is never good for your health :)

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