Jason Fung – How To Fast: A Beginner’s Guide

Dr. Jason Fung is a kidney specialist, author and proponent of intermittent fasting. He is an advocate for using fasting as a tool to combat obesity and type 2 diabetes – but how does he recommend approaching fasting as a beginner?

The Canadian nephrologist is the author of the books "The Obesity Code", "The Complete Guide to Fasting" and "The Diabetes Code". He argues that intermittent fasting is a better method than a standard calorie-reduced diet at reducing body fat, tackling obesity and type 2 diabetes.

In this article we’ll look at Dr. Jason Fung’s reasoning behind advocating intermittent fasting as a tool to lose weight and how he recommends people start fasting as complete beginners.

What is Fasting?

Fasting is voluntarily abstaining from eating food for prolonged periods of time. Historically, fasting has most commonly been related to religion with Muslims fasting during Ramadan, Christians fasting during lent, and Jews fasting during Yom Kippur. In recent decades, research has found that longer periods of fasting and intermittent fasting can provide many health benefits.

Intermittent fasting is the practice of alternating between periods of eating and fasting. People often eat in a specific window of time such as 8 hours and the remaining 16 hours they are fasting. Cycling between periods of eating and fasting can help to regulate insulin levels, support weight loss, and improve metabolic health.

The Health Benefits of Fasting

Studies have shown that fasting can provide a wide variety of health benefits. Fasting can promote weight loss, improve insulin insensitivity, reduce inflammation, regulate hormones, improve heart health, repair damaged cells, improve digestive health, and increase longevity.

Dr. Jason Fung says: “There are many great reasons to fast. Probably the most obvious one is to lose weight, and it’s a great way to lose weight—after all, if you don't eat, you’re going to lose weight. But there are a lot of other health benefits to fasting. You can reverse your type 2 diabetes—if you don’t eat, your blood sugars will fall, which will allow you to manage your blood sugars without taking medications. If you reduce your weight and reverse your type 2 diabetes, that’s going to put you at far less risk of diseases like heart disease, stroke, and cancer.”

People who take part in longer periods of fasting or intermittent fasting report they have higher energy levels and feel better in themselves compared to when they eat three or four meals per day.

The fasting expert says: “Many people feel better when they’re fasting—that’s why people often refer to it as a cleansing period or detoxification. Many find that they have more energy and feel they can think more clearly when fasting, and there are good reasons for that. Fasting also has more practical benefits—it’s a way to save time, money, and simplify your life.“

How to Start Fasting

Dr. Jason Fung recommends easing yourself into fasting to allow your body to adjust to it. You can then start fasting for longer periods He says: “If you’re just starting to fast, I would recommend starting by cutting out snacks for a week, just eating breakfast, lunch, and dinner. Then, you can progress to a 16-hour fast or time-restricted eating. During that period, you might allow green tea, herbal teas, and coffee with a little bit of cream but no sweetener. This is a very lax variation just to let you get used to it.”

Once you’ve cut out snacks and tried intermittent fasting for a couple of weeks you can then try longer periods of fasting if you wish. Dr. Fung explains: “If you're getting great results, continue—there’s no reason to stop. If you're not getting the results you’re hoping for, you can slowly change to a longer fast or maybe more of a classic water-only fast. But remember, whatever you do, make sure you’re staying safe and healthy, feeling well, and keep on going.”

It's important to be mindful of how you are feeling during intermittent and longer periods of fasting. Remember that you are in control and can stop at any time if you feel you need to. Dr. Fung says: “Don’t forget that you're always in control of this process. You can start fasting at any time, and you can stop fasting at any time. If you don't feel well, you can stop. If you do feel well, you can start. You can do more or less—it's always voluntary, and that's the key difference between fasting and starvation.”

How Long Should I Fast?

Once you’ve familiarised yourself with fasting to some extent you may want to start fasting for longer periods. There are three main options: The first being fasting for a set number of hours (intermittent fasting) each day e.g. fasting for 14 hours and eating in a 10-hour window. The second option is to eat one large meal per day where you would eat your allotted number of calories in one sitting and fast for the remainder of the day, the third option is a classic water fast where you drink only water and eat no food for an allotted amount of time. This could be 24, 36, 48 hours or even more as you become more experienced.

Dr. Jason Fung says: “How long you fast is completely up to you. You could just fast from dinner until breakfast the next day—that's 12 or 14 hours. You could go to 16 hours, which is called time-restricted eating. You could go to 24 hours, like a one-meal-a-day schedule, or you can do multiple-day fasts.”

He continues: “You can really fast for any period of time, but two popular regimens are time-restricted eating and a 24-hour fast. Time-restricted eating, also called 16:8, means you fast for 16 hours and eat during an 8-hour window. For example, you might start eating at 11 AM and finish at 7 PM, then fast after 7 PM. The 24-hour fast, also called one meal a day, involves eating once in a 24-hour period, such as from breakfast to breakfast or dinner to dinner. These fasts are very popular. Generally, the longer the fast, the less often you might do it. With time-restricted eating, you might fast 6 to 7 days per week, while a one-meal-a-day schedule might be done 3 to 4 times a week. But there’s nothing stopping you from doing more or less according to your needs.”

When You Shouldn’t Fast

For the majority of people, it is safe to take part in intermittent and longer periods of fasting, However, it is not recommended for children, pregnant women, or women who are breastfeeding. It’s also not recommended for anyone who is underweight.

Dr Fung explains: “There are some people who shouldn't fast. Remember, when you're fasting, you're not eating, so there are no nutrients. In certain conditions, it's crucial to get enough nutrients—like if you're a child, you're growing, or if you're pregnant or breastfeeding. In these cases, it’s very important to get enough nutrients, so those people should not do long fasts.”

He continues: “There are also other situations where fasting might not be appropriate. If people are underweight or malnourished for any reason, nutrients are very important, and fasting isn’t recommended. However, in most other cases, for adults, anyone can fast. In some situations, you should talk to your doctor, especially if you're taking medications. Some medications need to be taken with food, so you should discuss with your doctor how to adjust them so you can fast. If you're on medications that affect your blood sugar, make sure to consult your doctor. If you have a history of eating disorders or anorexia nervosa, you should also be cautious and speak to your doctor.”

Dr Jason Fung’s Final Fasting Tip

“Make it a habit. Just remember that everything is hard when you get started—you're not used to it, and everything seems difficult. But if you keep doing it over and over again, you get used to it.”