The Complete Guide to Fasting by Jason Fung, M.D.

June 12, 2022

The Complete Guide to Fasting by Jason Fung, M.D.

A comprehensive look at the practice of fasting, including reasons to fast. different ways to fast, how to get started, how to get through your fast, and how to comfortably end your fast.

Hunger and not eating is more of a psychological and cultural issue than a physical issue. Yes, we do get hungry, but it's more because we're programmed to eat at certain hours or a certain number of times per day, than because of a physical need. The longer you fast, the easier it becomes - the second day of a fast tends to be the most difficult. Practice helps: the more frequently you fast, the easier it gets. It's like getting weight loss surgery without the operation.

Yes, you can miss a meal (or two or three) without passing out or suffering serious health consequences. People have been fasting for thousands of years for religious and health reasons. Most people have had to fast at some point in their lives, for example, before having a medical test or surgery. Unless your body fat is below 5%, even the most elite athletes carry enough stored calories to last a month or two without eating.

Fasting allows your body's insulin levels to drop, so that you can burn stored fat for energy. Snacking constantly keeps your insulin high, which can lead to insulin resistance or type 2 diabetes.

Positive aspects: it's free - no special food to buy, no pills, no exercise equipment, no special clothes needed; almost everyone can do it - no training required - the book lists people who should not fast or should only fast under a doctor's supervision (the elderly, the very young, pregnant women, people with certain health conditions); it can be adjusted to fit into anyone's schedule or preferences - you fast on days when you know you're not going to a banquet or out with friends for dinner; you can make your non-fasting meal whenever you want, so if you love breakfast, you can schedule your fast so that you can eat breakfast; it's time-saving since there is no special meal prep required.

I am currently doing a 23-1/2 hour fast daily for weight loss. I have my daily meal in the evening around 6:30 p.m. and make sure I finish before 7 p.m., trying to stay with a low carb/high fat diet. This is just my preference - I feel better when I eat this way but you don't have to follow that particular eating plan. A LCHF eating plan means you take in fewer calories from carbohydrates and sugars, so although there may be an initial insulin release, your insulin level will drop quickly. But I've also done a 36-42 hour fast with no difficulty. As long as my weight loss continues on my current regimen, I'll stick to that but once my weight loss slows or stops, I'll switch to the 36-42 fast for a week, then go back to the 24 hour fast. You have to trick your system sometimes.

I don't know that I agree with everything in the book, such as cutting out things like artificially sweetened no-cal beverages. I avoid artificial sweeteners just because they are chemicals but I wouldn't necessarily tell everyone they can't have them, especially if it will help you get through your fast.

Lots of good information. I recommend it if you are at all interested in getting started with IF.