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In the Posts #63 and #64, I described that all fasting methods consist of some variations of these variables:

  1. What you eat or not eat,
  2. How much you eat or not eat,
  3. When you eat or not eat, and
  4. How frequently you repeat the process.

And, with these variables you can make all kinds of combinations. For example, you may have seen or heard of the following popular combinations:

  1. Water only Fast for, say, 1, 3, or 5 consecutive days; alternate day fasting; 5:2 fasting: fasting for 2 days and eating the other 5 days of the week.
  2. Calories Restricted Diet: 20% fewer calories per day, e.g., 1,600 calories per day when 2,000 is your regular intake
  3. Time-Restricted Feeding: 8:16 fasting: eating for 8 hours and fasting for 16 hours; 4:20 fasting, where you eat for 4 hours and fast for 20, etc.
  4. Fasting-Mimicking Diet: During fasting, you still eat but with certain restrictions on carbs and protein, so your body feels as if you are fasting.

So, what option is optimal for you or me, depends on a variety of variables including: state of your health, state of your fitness, your goals, your ability to follow the process in the short term or long term, any medicines you are taking, age, BMI.

There are a couple of important principles to remember while fasting.

Our bodies have Multiple Energy Sources: a) immediate energy from the food we eat, b) Glycogen stored in liver, and c) fat stored in the body, and d) lean body mass, and e) cellular debris. In different situations, body dips into appropriate energy source.

Chronobiology or body’s circadian clock dictates metabolism. For most people, metabolism is higher in the morning until early afternoon. So, it is better to eat heavier meals in at breakfast or lunch then at dinner.

The benefits of long-term fasting are numerous, seems almost too good to be true. But all theses have been demonstrated in research and personally I have experienced these:

  1. Lose weight
  2. Lose body fat, especially visceral fast, while retaining lean body mass
  3. Reverse diabetes, hypertension, lower LDL and many other health issues
  4. Become appreciative of tastes and smells of food
  5. Start to eat more mindfully
  6. Learn not to panic if food is not immediately available when feeling hungry
  7. Spend less time and money on food
  8. Improved mental and emotional outlook
  9. Increased lifespan and healthspan

Now for what works, what does not and how to make it work for you.

  1. Calorie Restricted Diet is the least effective for major weight loss: An important principle is that 1 pound of body weight does not always equal to 3500 calories. If you have tried to lose weight by counting calories, you know that by eating fewer calories by the same amount, you lose less weight in the second month than the first, and you less weight in the third month than the second and so on.

In fact, per Pennigton Biomedical Research Center Predictor Calculator, if I were to reduce my daily intake by 500 calories and keep it for a year, my weight loss over 12 months would look like the following:

Weight Predictor

As you can see from the chart, it gets harder and harder to lose weight by reducing number of calories and easy to hit a plateau.

  1. Calories restricted diet, however, does seem to offer benefits of both health span and lifespan 
  1. All other types for fasting are effective in weight loss and other benefits. What will work for you, depends upon your tolerance. 
  1. A good strategy often is to start with Time Restricted Feeding, work up to one or more days of water fasting or Fasting Mimicking Diets (FMD).

My wife Kimberly and I started with becoming conscious of how many hours we did not eat every day. And, then we tried to stretch that period to at least 12 hours every day and longer when possible. 

Next, we started with water only fasting for one day a week. For us, from Friday after dinner to Saturday dinner worked.

We did one-day-a-week water only fasts for about 4 to 5 weeks. We were working ourselves up to a 3-day and then a 5-day water only fast, but then we came across fasting mimicking diet programs. One such program is in the book: Grow a New Body, by Dr. Albert Villoldo.

Grow a new body

So, we moved to 5-day programs of fasting mimicking diet. We are doing the ProLon protocol that consists of prepackage food and supplements developed at the University of Southern California by Valter Longo and explained in his book, The Longevity Diet . We like the results.

The longevity Diet

Fasting does have side-effects that include headache, lethargy and low energy. But these tend to resolve themselves.  Drinking lots of water and staying hydrated really helps. On a longer fast, first day tends to be the most difficult.

And, finally, fasting is not recommended in the following situations,. It is best to check with your doctor and work under doctor’s supervision while fasting:

  1. For pregnant and lactating women or children
  2. If you are on any medications, especially for diabetes and hypertension
  3. If you are underweight
  4. If you are over 70 years old


  1. There are many benefits of fasting, from more mindful eating to reversing diseases and living longer.
  2. Several variables make up a fasting protocol: what, how, when and how frequently you eat or not eat.
  3. There are many types of fasting: water only fasts, calories restricted diet, time-restricted feeding, and fasting-mimicking diet. What is optimal for you depends on a number of factors related to your health, fitness, and goals.
  4. Three general principles that you can use as guide to choose a protocol that may best suit you are: multiple sources of energy, autophagy and chronobiology.
  5. Calories restricted diet is not the best for weight loss for long terms. However, you do get benefits of healthier and longer life
  6. You can start with time-restricted feeding, extend periods of not eating and then work up to multi-day fasting.
  7. Fasting mimicking diets are great ways to have the benefits of longer fasting.
  8. If you have any medical issues, fast only under the care of a medical doctor.

What do you think?

Have you an experience with fasting? What worked or not worked for you? What benefits or difficulties you faced while fasting?

I and the readers of this blog would love to hear from you and learn from you.

Please click on Comment to leave your comments or question so others can benefit from your input.