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February 27, 2018

***We highly recommend listening to the 60 minute podcast: “Bulletproof Radio Why YouShouldn’t Fear Fasting” as an adjunct to this handout

Fasting has been around for centuries for spiritual reasons, recommended by Buddha, Jesusand Muhammad. It has been recommended as early as 400 BC by Hippocrates for healthreasons and this sentiment echoed by Paracelsus, Benjamin Franklin and Mark Twain.

Health benefits of fasting:

  • improves memory and concentration
  • induces weight and body fat loss
  • lowers blood sugar levels
  • increases insulin sensitivity
  • increases energy
  • iowers blood cholesterol
  • prevents Alzheimer’s disease
  • extends life
  • slows down the aging process by promoting autophagy, the body’s process of cellular
  • cleansing. Damaged cellular parts are discarded so that they can be replaced by new ones.
  • decreases inflammation
  • decreases bloating by eliminating excess salt and water

Advantages of fasting:

  • it’s simple
  • it’s free
  • it’s convenient
  • it’s powerful- it works when other diets fail
  • it’s flexible- you can fast or stop fasting anytime. If at any time you do not feel well (not just hunger pangs) you can eat.
  • it works with any diet

What happens when we eat: eat food— increase insulin— store sugar in liver—produce fat in liver

What happens when we fast: no food—decrease insulin—burn stored sugar— burn body fat

  • adrenaline increases, giving you energy and speeding up metabolism
  • growth hormone increases, increasing muscle mass and decreasing body fat


1. Fasting puts you in starvation mode

Starvation mode refers to the idea that our metabolism slows down when we are not constantly eating. Studies demonstrate that this happens when reducing calories but not with fasting. In fact, fasting has been shown to increase metabolism! If we do not eat, the body cannot decrease metabolism to 0 (we have to burn some calories to just to stay alive). Instead, the body switches energy sources from food to stored body fat.

2. Fasting makes you burn muscle

It would not make sense to store fat as an energy source and then turn to burning muscle when food is not available. It would be like storing firewood, but then burning your furniture instead, when heat is needed. We actually lose less muscle during fasting. Remember that fasting stimulates growth hormone secretion, which helps maintain lean body mass. Only when body fat falls below 4% (much lower than the typical 8% body fat percentage of elite athletes) will the body turn to burning protein from muscle for fuel.

3. Fasting causes low blood sugar.

Our bodies are adapted to not having food always readily available. If food is not available, our body will derive the glucose by breaking down glycogen (short-term glucose storage) in the liver. After the glycogen stores are used up, the liver begins making glucose by breaking down stored body fat.

4. Fasting results in overeating

Studies do show a slight increase on the first day after fasting (for example an almost 500 calorie increase from 2436 to 2914 after a 1 day fast). If you consider that one might otherwise consume 4872 cal over those 2 days, there is still a net deficit of 1958 cal.

5. Fasting deprives the body of nutrients

During fasting, the body holds on to much of the essential nutrients/fatty acids/amino acids and recycles them, instead of excreting them. For fasts lasting longer than 24 hours, a multivitamin prevents any nutritional deficiencies.


During any of the following fasts, bulletproof coffee (coffee with butter and/or MCT oil), plain coffee or tea is allowed. Unlike proteins and carbohydrates, fats elicit a minimal insulin response so the fasting state is still considered maintained. For longer fasts, homemade bone broth is acceptable, but does elicit a little bit more of an insulin response (and hence may inhibit autophagy) than fats, since bone broth has some protein. However, the insulin response will still be considerably lower than an actual meal, so if that will enable you to fast for a longer period of time and weight loss is your goal, then use the bone broth.

1. Intermittent fasting

You can fast anywhere from 12-23 hours/day. We tend to recommend 16 hour fasts becausethey are more effective than 12 hour fasts but more doable than 23 hour fasts. This means limiting your eating to an 8 hour time frame, like 11am-7pm or 9am to 5pm. The latter will have a greater benefit than the former because insulin sensitivity is lower in the evenings than in the mornings. Consequently, it takes more insulin to normalize blood sugar after a meal ingested at 7pm vs 5pm.

2. 24 hour fasts

This involves fasting from dinner to dinner (or breakfast to breakfast, whatever your preference), so you are still getting 1 meal daily. For example, if you finish dinner at 7pm on one day, you fast until 7pm the next day. An advantage to this is you can still sit down with your family for a meal. These can be done daily or as often during the week as you would like. Perhaps 1-3x/week would be more palatable.

3. 5:2 diet

This consists of 5 normal eating days and 2 low calorie (500-600calories) days, which can be consecutive or spaced apart. The 500-600 calories can be eaten in a single meal or spread out over the course of the day.

4. Alternate-Day fasting

This involves fasting every other day. As in the 5:2 diet, 500-600 calories are allowed on fasting days.

5. 36 hour fasts

With this fast you skip meals for 1 entire day. For example, if you finish dinner at 7pm on day 1, you fast through all of day 2 and not eat until 7am on day 3.

6. Extended fasts

You can fast for as many consecutive days as you desire to achieve weight loss or health goals. A good multivitamin will prevent any nutritional deficiencies.


1. Eat whole, unprocessed foods
2. Avoid sugar/sweet tastes
3. Avoid refined grains
4. Eat a diet high in natural fats
*** at Tustin Longevity Center, we encourage patients to keep carbohydrates under 50 grams/day (<30gms/d for cancer patients)


Do not fast if you are:

1. Malnourished or underweight, with a Body Mass Index below 20 (up to 24 hour fasts would
be ok, but longer fasts are not advisable)
2. Under 18 years old
3. Pregnant
4. Breastfeeding
Consult your doctor if you:
1. Have gout
2. Are taking medications
3. Have diabetes
4. Have gastroesophageal reflux disease
*a brief synopsis of The Complete Guide to Fasting by Jason Fung, MD