Fasting: Hype or Health?

Is Running on Empty Good for the Body?

“I fast for greater physical and mental efficiency.” 


Articles on fasting are appearing in virtually every media outlets. Whether you want to lose weight, improve your health, or seek spiritual enlightenment there seems to be a fasting program for you. Fortunately, the timeless tradition of intermittent fasting is now being validated my modern medical science. Let’s take a look.

What is Fasting?

Early in human evolution, fasting was simply a part of the feast or famine cycle that impacted all humans as a result of periodic disruption in food supplies. During the agricultural revolution, food became more readily available and famine-induced fasting became less frequent. 

Fasting has long been used by most religious practices for emotional and spiritual cleansing. It has also been used to cleanse physical body as well, with claims of rejuvenation. Now, there is scientific evidence that intermittent fasting has dramatic impacts on the body that not only improve health but vitality as well. Modern technology and scientific ideology are beginning to unravel the mysteries of how fasting clears the “fog” while providing renewed “energy” as described by 13thcentury mystic and poet, Rumi, in his poem, Fasting.


There’s hidden sweetness in the stomach’s emptiness.
We are lutes, no more, no less. If the soundbox
is stuffed full of anything, no music.
If the brain and belly are burning clean
with fasting, every moment a new song comes out of the fire.
The fog clears, and new energy makes you
run up the steps in front of you.
When you fast, good habits gather like friends who want to help.
Fasting is Solomon’s ring. Don’t give it
to some illusion and lose your power,
but even if you have, if you’ve lost all will and control,
they come back when you fast, like soldiers appearing
out of the ground, pennants flying above them.
A table descends to your tents, spread with other food,
better than the broth of cabbages.


Fasting is simply the process of restricting external caloric intake from food and beverage sources so that the body can shift to metabolizing its own unused energy stores, primarily in the form of fat. Fasting is not the same as detoxification, which has been popularized in mainstream media. However, detoxification does occur as part of a healthy intermittent fasting program.

The longest medically supervised fast was 382 days in an obese 27-year old male patient thus demonstrating the adaptability of the human body to caloric restriction. Obviously, this type of prolonged fasting should never be done without medical supervision. More commonly, fasting is done intermittently and in intervals as short as 12 – 16 hours daily to intermittent bouts of fasting that last 1-7 days in which the individual consumes less than 800 calories a day while ensuring adequate hydration with water. Although, there seems to be an A-to-Z list of fasting protocols on the internet and social media, there really are four common approaches that have been studied in both animals and humans. The common feature of most fasts is that they are intermittent and of limited duration.

Common types of intermittent fasting:

  • Alternate-day fasting: Individuals alternate regular eating with restricted eating every other day. On the restricted eating (fasting) days there is usually only one meal of 300-500 calories.
  • 5:2 fasting: On a weekly basis, the individual eats a normal diet 5 days a week and fasts for two days consuming only one small 500-calorie meal. These days can be continuous or spread out during the week.
  • Periodic fasting: This fast can is perhaps the most variable in that it can be done as frequently as once a month to once a year or less. Most often, a period of at 3-5 continuous days is used when food is avoided or at least limited to less than 800 calories a day. These can range from complete water fasts, as is typically done with ceremonial fasts such as vision quests, to subsidized fasts such as the newer “fasting mimicking diet” where energy intake is stepped down over the fast with subsidized plant-based foods low in carbohydrates, proteins and calories.
  • Time-restricted feeding: Since individuals are in the fasting state when they sleep, this fast simply adds time before and after going to bed. Typically, the non-eating pattern is in the range of 8-16 hours daily. For most this means not eating 3-hours before bedtime or immediately upon awakening.

As a result of calorie restriction, fasting results in the shifting of fuel sources for metabolism. Normally, most fuel we need comes from the external calories we consume in the form of food and beverages. Any excess calories go into storage. During fasting there is a shift in fuel source from external calories to internal stores, mainly the triglycerides stores in fat cells. The fatty acids released can be used as energy and also travel to the liver where they are converted to ketone bodies. The ketone bodies then travel through the blood to fuel the heart, brain and muscle. 

Unlike the ketone producing diet, known as the ketogenic diet, there is no need to adhere to a strict dietary regimen long term. Intermittent fasting is rapidly becoming popularized since it can be done conveniently and achieves similar metabolic results to the ketogenic diet. 

If fasting is not done properly, then the body may turn to the muscle, which generates fuel through the breakdown of proteins and results in loss of lean body mass. When fasting, you certainly want to avoid loss in lean body mass, which includes the weight of all your organs, your skin, your bones, your body water, and your muscles. Rather, you want to see body fat mass decreasing and the shrinking of fat cells rather than loss of muscle mass. This is where the science is beginning to unravel the mysteries of fasting.

What are the Benefits of Intermittent Fasting?

When performed in a healthy and safe way fasting has numerous benefits. As a result of shifting fuel to from carbohydrates to fat stores, many changes occur in the body that aid its repair and regenerative capacity. Not only does fasting change your biology it can help with mental clarity and vitality. The primary benefits of intermittent fasting include:

  • Healthy weight management
  • Healthier aging and vitality
  • Improved heart health.

recent review of intermittent fasting summarizes both the benefits and potential harms in fasting. The latter is usually a result of poorly timed or unhealthy patterns of fasting.

The benefits of fasting include:

  • Improved weight loss
  • Detoxification
  • Reduced inflammation
  • Improved digestive health
  • Reduced blood glucose levels
  • Reduced blood glucose levels
  • Enhanced immunity
  • Reduced blood pressure
  • Reduced cravings
  • Healthier brain.

The dangers include:

  • Low blood pressure
  • Low blood sugar
  • Excessive weight loss
  • Nutritional deficiencies.

As a result of these benefits in aiding successful aging, intermittent fasting may potentially help prevent and reverse many chromic conditions such as Alzheimer’s disease and other neurodegenerative disorders, multiple sclerosis, cardiovascular disease, diabetes and other metabolic disorders, autoimmunity and cancer. The dangers can be avoided by working with an individual fully informed about the science of fasting and your current health status.

How do I Fast?

As a physician interested in health and wellbeing, I have been researching and experimenting with intermittent fasting. I have begun to incorporate fasting into my lifestyle in several different ways:

  1. Time-restricted feeding (10-16 continuous hours): I typically aim for 8 hours of sleep daily and don’t eat 3 hours before bedtime. Other than water, I usually don’t eat anything for at least one hour after waking up in the morning. This gives me a twelve hour fast most days of the week.
  2. Periodic fasting (3-5 continuous days): This has been done a couple of different ways and at a frequency of at least once a year for both physical and spiritual purposes. My initial goal is to use intermittent water fasting for 3-5 days at least four times yearly. This is done at the beginning of each season to honor what the previous season provided, while allowing purification and renewal to begin the new season. More recently, I have added the new fasting mimicking diet (FMD) as the recent studies are encouraging.

The fasting mimicking diet was developed by Valter Longo, PhD at USC Leonard Davis School of Gerontology after decades of basic science research. A goal was to be able to feed the body while still keeping the cells in a metabolically fasting state. His group has formulated a plant-based commercially prepared diet high in polyunsaturated fats and low in carbohydrates, protein and calories. His stepped dietary program is highly palatable and hunger is not an issue. A recent study in mice showed that the fasting mimicking diet magnified the beneficial results of chemotherapy. Another recent study in humans showed benefits in weight loss that was sustained for 3 months after completing the program and associated with improvement in cardiovascular risk factors.

Benefits of Fasting Mimicking Diet (FMD)

  • decreases body fat
  • decreases body weight, which is sustained at least 3 months after resuming a normal diet
  • preserves lean body mass
  • improves energy levels
  • maintains healthy fasting blood sugar
  • lowers blood pressure
  • lowers cholesterol and triglycerides
  • reduces inflammation as measured by C-reactive protein
  • stimulates stem cells
  • reduces insulin-like growth factor

My Recommendations: 

So, I recommend that individuals work with a knowledgeable health care provider and explore the various intermittent fasting protocols to discover for themselves what works and is sustainable for a lifetime. For most, this will be either time-restricted feeding most days of the week or some form of intermittent fasting such as the fasting mimicking diet or the 5:2 diet. 

Join us for Be Well, FAST – Traverse City’s First Fasting Mimicking Diet Week or contact my office to schedule a consultation to review your health history and customize a program for you.

Transitioning from a Fast

There simply is no better way to nourish human and planetary heath then transitioning to a whole food, plant-based diet. The scientific evidence is overwhelming and continue to support the need to increase consumption of vegetables, fruits, whole grains and legumes while eliminating most processed foods and all factory farmed animal products.

If you need guidance with this transition please feel free to contact my office to schedule a consultation to review your health history and customize a dietary transition program for you.

A Word of Caution about Fasting:

Fasting should be done with caution especially if you have any metabolic conditions that require medical attention. Fasting should not be done in children, the elderly, or women that are pregnant or nursing. Medical supervision is recommended for anyone with diabetes, type I to type II, cardiovascular disease, cancer or chronic illnesses.

“Fasting is the first principle of medicine: Fast and see the strength of the spirit reveal itself.”