The Complete Guide to Fasting by Jason Fung MD with Jimmy Moore is an excellent book to learn about fasting.

Introduction

Some time ago I was looking at ways to improve my metabolic health, insulin sensitivity and stimulate autophagy. I came across fasting as a helpful tool and I looked at articles, videos to learn more. I came across Jason Fung’s videos online and looked up the book “The Complete Guide to Fasting by Jason Fung MD with Jimmy Moore” which this article is about. I am glad I read it. It is a really good book to learn about fasting, obesity, diabetes, the biology on how energy is handled by the body and some related processes.

I am going to divide the learning from the book into 6 areas. These are the biology behind fat storage, diabetes etc, why fast, how safe is fasting, how to prepare for a fast, what to expect and keep in mind when in a fast and how to break a fast. The following sections expand on these.

Biology behind fat storage, obesity, diabetes and metabolism

I really liked the information and explanations given in the book regarding the biology behind fat storage, how insulin works, different types of diabetes, calories in calories out model etc. If you haven’t come across these before it makes for a fascinating read. Having a basic understanding of these topics helped me realize the teas, juices etc that are advertized as helping in losing fat may not even work or have the opposite effect. I think it is good to know these things so we are not easily misled.

Why fast?

The book talks about the biology behind insulin resistance and type 2 diabetes. It makes a bold claim that type 2 diabetes can be cured. You may be surprised to hear that but with the logic the book presents, I found it convincing. The book presents the way to reverse type 2 diabetes is to lower insulin levels in the body. It is because high insulin levels is a major factor behind type 2 diabetes. One way of reducing insulin is by choosing to have food that doesn’t raise insulin that much. The diets that help with it are low carb and keto diets. The author is a doctor and suggested it to his patients for type 2 diabetes and obesity. The patients found it was complicated and difficult to follow. Take for instance the complications on the advice to not eat bread. Someone could think, the doctor told me not to eat bread so I guess naan is fine. The book talks about people filling their food diaries/journals with noodles and naan when they were told to avoid/limit bread. Fasting on the other hand is simple to understand and free, no need to buy grain free flour, learn low carb recipes or wash dishes. Most importantly fasting is very effective in reducing insulin levels with no adverse side effects when done properly.

How safe is fasting?

Fasting is practiced by different cultures and religions around the world for spiritual, cleansing or some other reasons. It has that history behind it that speaks to its safety when done properly. You may have heard about muscle wastage and starvation associated with a lack of food. The book explains why that might not happen if your body fat percentage is above 4%. The muscle wastage stage is called starvation mode. If there is sufficient stored energy then we go into a fasted state not starvation mode. The book talks about the differences between them and why it is probably not a concern for the majority of us.

The books cautions that it is not advisable for children, people who are malnourished, pregnant and breastfeeding women to fast. It also notes some medical conditions for which fasting is not recommended or the situations where you need to talk to your doctor before doing it. If you are concerned about electrolytes balance or ketoacidosis then there is good information about these in the book. Generally speaking, you don’t need to worry about those. The book mentions that compared to surgical procedures like bariatric surgery fasting is less complicated with no adverse side effects. In short, our bodies have the ability to store certain things and use it when in need. Fasting gives an opportunity for our body to tap into its stored reserves which in general, is safe.

How to prepare for a fast?

Being prepared to handle the hunger or the feelings of emptiness in the stomach is very helpful to set realistic expectations going into a fast. The book discusses these in detail and have accounts from people about what they did in certain situations. Some of the mechanism involved in triggering hunger are also discussed. I found the mechanism by which the body triggers hunger even in the presence of enough stored fats, when insulin levels are elevated, fascination. Since high insulin levels make using the stored energy and fasting difficult, the book suggests to ease into a fast. It means starting with smaller duration fasts, slowly going up to the desired duration and a change in diet to low carb or keto to reduce insulin levels and make fasting easier.

What to expect and keep in mind when in a fast?

Depending on the type of fast being considered there are things that can and cannot be consumed to maintain the fast. For example water fasting involves the consumption of water for the duration of the fast and nothing else. There is juice fasting, fat fasting and other kinds. The fasting method the author is suggesting can include tea or coffee, bone broth and multivitamins. Non caloric sweeteners like in diet cola is not recommended due to the chances of it causing hunger. There are mental components to fasting like habit, hunger or emptiness that will be there. The book shares some perspective on these aspects of it. Keep in mind, if it feels too much, stop the fast and try again later.

How to break a fast?

The book recommends to break the fast with a small dish or meal and wait 30 minutes to an hour before the main meal. Longer duration fasts calls for some precautions but shorter ones, that is less than 24 hours, doesn’t need any special precautions. There is something called refeeding syndrome that becomes relevant for certain long duration fasts and it has to do with electrolyte balance in our bodies. The book explains it and it is great to know about it and how to prevent it. There is going to be hunger as can be expected but it is important to eat normally after a fast for the expected benefits.

Conclusion

The book is packed with information on fasting and the mechanisms involved in obesity and diabetes. I found it easy to read and understand. There is recipes in the book so if you are not sure what to eat on a low carb or keto diet there are some ideas included in the book. I think this is a very helpful book to learn not just about fasting but also about some important things about how our bodies work. I highly recommend it.

Book discussed

• The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting by Jason Fung MD with Jimmy Moore