Why The Best Way To Fast May Be Intermittent Fasting

In my last post, I talked about using fasting as a means to lose weight.

When you fast, you forgo food for a designated period of time. Almost every culture and nation has practiced fasting at some point or other. Sometimes it’s been incorporated into a religious tradition. Other times, individuals have used it to express their opposition to a political situation. And many cultures have used the fast as a medical tool.

Advocates of fasting emphasize how good it is to give the body a break now and then from the stressful process of digestion. Fasting allows the liver to more effectively detoxify the cells, which can become overloaded with toxic byproducts of the metabolism. After a fast, your digestive tract is free of toxins, pathogens and waste matter, allowing you to make optimal use of nutrients consumed.

Detractors insist that the body is designed to dispose off toxins by itself without the need for a fast; that the body is exhausted of its calcium and protein during a fast, which can result in osteoporosis and muscle decomposition; and that fasting reduces the resting metabolic rate, which translates into rapid weight gain once the fast is over.

Remarkably, scientific animal studies have proven that restricted-calorie diets increase longevity. New research suggests that a reduced calorie diet combined with intermittent fasting results in a longer, healthier life for humans as well.

How Do We Define Intermittent Fasting?

It is the continuous and repetitive process of eating normally for a certain amount of time and subsequently fasting for a period of time. When you fast intermittently, you alternate between periods of non-fasting and fasting.

What Makes an Intermittent Fast Superior to a Traditional Fast?

First, intermittent fast is not about eating or avoiding specific foods, therefore you eat what you enjoy during non-fasting times. This is very important if you consider that most diets fail because they deprive people from their favorite foods. With intermittent diet you don’t get “diet fatigue” because you are not fasting continuously. Another advantage is that you don’t have to worry about counting calories. You just restrict them all at once during the fasting periods.

A great factor in favor of intermittent diet is its short duration. Because each fasting segment does not last more than 24 hours, your metabolism doesn’t have a chance to slow down. Furthermore, unlike tradition fast, you don’t worry about entering into starvation mode, which would be catastrophic for your muscles and your health in general. Finally, the short duration of intermittent diet eliminates the risk of nutrient depletion and ensures that your energy levels are not reduced. For all these reasons, intermittent fast is better than usual fast.

What Is the Impact of Intermittent Fasting on Health?

Excess weight increases the risk of several diseases, such as cardiovascular disease, diabetes and certain forms of cancer, to name a few. Overweight people who restrict their food intake and lose some of their excess weight lower significantly their chances of suffering from any of these diseases.

Here is the problem, though. Continuous energy restriction is not a sustainable form of dieting. Continuous food deprivation is actually the main cause dieters never get to comply with a diet for more than a few weeks or months at best.

Studies have shown that fasting in short spells separated by longer periods of habitual (ad libitum) food intake is equally or more effective than continuous energy restriction. Sounds complicated? Simply put, there is evidence that it’s better to abstain from food two days a week and eat at pleasure (but sensibly) the remaining 5 days of the week, than just restrict yourself to following a low calorie diet everyday.

Studies conducted in animals over the last 8 years have shown that intermittent fasting:

  • Reduces age-related cognitive impairment
  • Protects the heart
  • Improves insulin sensitivity
  • Prevents tumorigenesis
  • Delays the onset of prostate cancer
  • Prolongs survival
  • May have beneficial effects in the pathogenesis and treatment of multiple sclerosis

Researchers from the Stanford Medical School in California, noted health benefits that began in test animals in as little as two weeks after the commencement of an alternate-day fasting program. Their summary included a long list of disease conditions alleviated by intermittent fasting, and they suggested that this pattern of eating could be effective as a weight loss strategy.

For the study, rodents ate restricted calorie diets on one day, consuming less than half of their estimated daily requirement. The following day, the test animals were allowed to eat as much food as they desired. The research team noted marked health benefits. The list included resistance to allergies, asthma, infectious disease, rheumatoid arthritis and other autoimmune disorders, cardiac arrhythmias, and menopause related hot flashes. Insulin resistance was also improved. Further, the animals’ cognitive ability got better and they were impacted less by acute stress.

BDNF (brain-derived neurotrophic factor) levels were also found to have increased. This chemical is a neurotrophin that allows certain sections of the adult brain to grow new neurons. Humans with high levels of BDNF are less depressed and more intelligent. When test animals have been injected with BDNF, they experience improved insulin sensitivity, which allows them to lose weight. BDNF is a desirable brain chemical, which can be increased through intermittent fasting.

How Do I Perform an Intermittent Fast?

Although there are a number of different ways, three types of intermittent fast are the most popular.

1. Daily Fasting Method

On this protocol, food intake occurs for a block of time during the day. The popular Fast-5 Diet is a type of daily fasting. All foods are allowed, but they must be eaten during a 5-hour window (from 5 pm to 10 pm, for instance.) Fasting continuously for 19 hours is the key to this diet’s effectiveness. The intestinal tract remains empty for long periods of time and insulin levels are reduced. You won’t see significant weight loss until you’ve been on this diet for two weeks. After that, you should lose weight at the rate of about a pound per week.

2. “Eat Stop Eat” Method:

You devote one, two or three non-consecutive days of the week to fasting and exercise. The rest of the time you eat normally without restriction. When you fast, you consume water and black coffee exclusively. One pound of body fat is equivalent to 3500 calories. By alternating normal food consumption with a day or two of fasting, your weekly caloric consumption is decreased by at least 3500 calories. That means you lose minimum 1 pound a week.

3. Alternate Day Fasting Method:

On this protocol, there is one day of eating followed by one day of fasting. A technique that ensures that you never go an entire day without food is as follows: Start your fast after you have eaten dinner early, say about 6 p.m. The next day, you won’t eat until 6 p.m., at which point you’ll have dinner and start your day of eating. This fast has a couple of benefits. For one thing, it’s an easy way to ease into intermittent fasting. For another, you’ll enjoy health and weight loss benefits, while minimizing the sense of dread you might experience about the upcoming fast.

It appears that intermittent fasting can’t be beat for real long term weight loss and health. If you combined intermittent fasting with eating low carbs between the fasting periods, it wouldn’t be an overstatement to call yourself a fat furnace!

Author: Biologist Matthew Papa, PhD, worked as a postdoctoral research fellow at Washington University in Saint Louis, MO, from 2004 to 2010. He enjoys blogging about obesity-treatments and best weight loss programs.

Image credit:  Alan Cleaver

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About the Author

Biologist Matthew Papa, PhD, worked as a postdoctoral research fellow at Washington University in Saint Louis, MO, from 2004 to 2010. He enjoys blogging about obesity-treatments and best weight loss programs.

32 Enlightened Replies

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  1. Jennifer Gaughan says:

    This is very informative and helpful. I have shared
    it with others that want to get more into health and nutrition along with weight manangement.
    thanks Jennifer

    • Hey Jennifer,

      So glad you stopped by. I hope you and the family are feeling better.

      Thanks for sharing and chiming in!


    • shamika smith says:

      Hey E, I have been IF for the last 4 months with a 6/18 window and weight training my results have been amazing, I agree with you on everything your blog has stated. I wish I could post a pic but you can find me on yt @ssmith2141, where I coupon and on FB @shamika Smith in Dayton, OH.


  2. Bob Wells says:

    Great post, Dr. Papa.

    Intermittent fasting can be a great way to take off unwanted pounds. Research has demonstrated many of the benefits associated with intermittent fasting.

    You mention the option of fasting two days and eating five. Historically, this is what pious Jews did, fasting on Monday and Thursday. It’s amazing to see how many “new” concepts in medicine originated hundreds and thousands of years ago with the likes of the great Maimonides.

    Thanks again for the information.

    In good health,


  3. Curt says:

    I have recently become a huge fan of intermittent fasting, I never thought that i could feel this energetic on days that I don’t eat! I use a combination of the second and third methods that you have listed, that third one just doesn’t seem right to me…

  4. Val says:

    Interesting. I didn’t realize there were all these options for intermittent fasting. I used to fast, but got out of the habit. This is a good reminder to start again.

  5. Unicron says:

    I’m going to start the alternate day fasting for health. I will definitely reply back in a few weeks if everything goes good, I might reply if it goes bad.

    I’ve wanted to get into fasting for health and spiritual reasons for a while but couldn’t really get into it. I know I’m capable of the alternate day fasting and I’m hoping it will help me get to a point where I can try longer cleansing/spiritual fasts.

  6. Sandra says:

    I knew about eat stop eat form of intermittent fasting but not the others. I did this for awhile and it worked nicely and I felt good. For one reason or another I quit and simply haven’t been able to get back into this groove since. I’ll check out the other methods and see if one of them will do.

    Thank you.

  7. Jay says:

    Fasting weight loss methods are good but you have to keep a balance in the diet else you have to face serious health problems. Its one of the best way of weight loosing and it helps metabolism.

  8. Tatianna says:

    I kept giving this a try, and I just could’t go without food. All I could think of was eating, for some reason I also had severe mood swings from fasting. I guess it’s not for me.

  9. Jarret says:

    Mathew, this is a great overview of intermittent fasting. It’s a topic that I hadn’t read much about until lately.

    Evelyn, Lean Gains just joined our blog network. Martin’s a well-recognized guru of intermittent fasting. We’re excited about his blog joining our network as he has a HUGE following. He also has some very cutting-edge thoughts on diet and exercise.

  10. chioma says:

    Great post on fasting. I agree a lot on this post, fasting is a good way of helping our bodies detoxify itself naturally.

  11. Susan says:

    Awesome post on fasting. I am very familiar with the Eats Stop Eat fasting method but am happy to learn a few other ways to work fasting into my day. I believe in fasting so much that I actually prescribe it to my clients looking to lose weight or those who have crazy cravings for food that sabotage their weight loss efforts. It works really well!

  12. Patricia says:

    Some great information here. I have enjoyed both post on fasting from your guest poster Evelyn. Thanks
    Patricia Perth Australia

  13. Dandy says:

    Hi Evelyn,
    This post is packed full of helpful information. I’ve found that intermittent-fasting helps me maintain my weight loss. But I appreciate you mentioning the different methods of fasting. I will definatley try them out. It’s important for folks to find what works best for them. Thanks Evelyn!
    Take care,

    • Hi Dandy,

      Matthew did a great job on this article! 🙂

      That is great that you have found this type of fasting to help you.
      Thanks for stopping by and chiming in! 😉

      Take care,


  14. Matthew Papa says:

    I mean an Indian colleague.

  15. Matthew Papa says:

    Hi Sudeep,

    one of my colleagues at work would fast once a week, indeed. I learned quite a bit from him about eating healthy.

  16. TrafficColeman says:

    I hear lots of women talk about fasting, but I never really caught the whole story. Thanks to this post..I can better understand this new world, and I think its awesome people do things like this.

    “TrafficColeman “Signing Off”

  17. Sudeep says:

    Enjoyed this pose thanks for the material…
    In Indian culture normally we do fast at least once a week … now in a week one day every week is some times to be a day of fast both for spiritual reason and physical.
    Longer term fasting has never been recommended by Ayurveda.

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