Part Two of Jason Fung’s book: The Complete Guide to Fasting


As we discussed last month we are going to continue our discussion of Jason Fung’s book: The Complete Guide to Fasting. In the second section Dr. Fung discusses specifically the how to’s of fasting. 


Fasts are defined by what you can eat or drink on a fast & how long they are. To review, when fasting you are not taking in calories, yet it is important to drink fluids such as: water, tea and black coffee. There is some disagreement over artificial sweeteners as they can trigger the desire for more sweets in the body. It is generally thought that it is best to avoid them.


Shorter fasts are from 12-24 hours and longer fasts are more than 24 hours.  There are some types of fasts that are common to hear about and the author spends some time touching on them. First, a juice fast is not technically a fast as there are calories in juice so you are not getting the benefits of a non-caloric fast. Second, the fat fast has become popular specifically with bullet-proof coffee.  This is also not technically a fast because you are taking in calories. Although it was developed by researchers there has not been many subsequent studies to reinforce it. There are a lot of anecdotal success stories; such as helping to increase mental clarity and decreasing food cravings. A third fast that is common is called the fasting mimicking diet. It is a complicated regimen developed by researchers to get the effects of fasting without fasting. You eat less for 5 days every month and follow a very specific plan. There is not a lot of research to support it and it is quite complicated. 


Next the author expands on some best practices for fasting.  This includes putting lemon juice, mint, or cinnamon in water along with making sure to drink 2 liters of water and other fluids daily.   To help with variety, try infusing water with oranges, cucumbers, berries, etc. You can drink tea and add 1-2 teaspoons of cream or coconut oil.  If you do hit a plateau then go back to a water only fast. If you are doing a longer fast than making and drinking homemade bone broth can be helpful to maintain electrolyte balance. 


The author goes on to describe intermittent fasting or time restricted eating patterns. 

12 hour fast:  can be good for prevention but may not work for weight loss. 

16 hour fast:  7pm-11 am or an 8 hour window to eat when done in conjunction with a low carb diet can result in slow and steady weight loss. 

20 hour fast:  can be helpful for weight loss as well.  

He reiterates the importance of eating nutrient dense foods during the time periods when you are eating. 

Longer periods of fasting results in more weight loss and decreased insulin. He stresses the importance of being followed closely by a medical practitioner if you have type 2 diabetes. He also discusses how you should stop fasting if you don’t feel well at any point.


Here are other beneficial fasting options:

Fasting from 7 pm to 7 pm 2-3 times weekly can give you huge health benefits and increased weight loss.  

5:2 fast- 5 days with normal calorie intake and 2 days with greatly reduced calorie intake can be another approach.  

A 36 hour fast is great for diabetics when working with a doctor or provider. This means you fast from 7pm on one day until breakfast 2 days later.  The author uses it 3 times a week for his diabetic patients. He discusses a 42 hour fast which many of his patients do by adding an additional day on to a 16 hour day fast.  This can also be a great adjunct to help with weight loss and decrease insulin levels.

A prolonged fast up to 2 weeks can also be beneficial. The hardest period of time is the first 2 days. Then, typically the hunger pains are gone and people feel good.  This relates to his conversation about ghrelin, which is the hunger hormone that follows a circadian rhythm. If you ignore it- it will dissipate. You may feel hungry, but if you feel faint, unwell, or nauseated then stop.  2-3 day fasts are common and helpful, but why not move to the 7-14 day fasts since you’ve already got through the worst 2 days. STOP at 14 days to decrease risk of refeeding syndrome due to lack of electrolytes which can cause the body to power down. This could even lead to a heart attack. To avoid refeeding syndrome drink bone broth, water, and take a daily multivitamin. 


Let’s wrap up with a few tips for fasting from the book!  

  1. Drink water
  2.  Stay busy
  3.  Drink coffee
  4.  Ride the waves of hunger
  5.  Don’t tell others you are fasting
  6.  It takes one month to adjust
  7.  Eat nutrient dense foods when you do eat
  8.  Don’t binge
  9.  Make fasting fit for your life 
  10.  Break your fast slowly with a nutritious snack or small dish then wait 30-60 minutes to eat your regular meal. This is especially important for fasts over 24 hours. 


In conclusion, fasting is easy and flexible and can be a great addition to your weekly regimen. If you are interested, please schedule an appointment with Dr. Shelley Meyer or Sarah Julianelle, NP to come up with a plan that would work best for you