An IF is a fast of 24 hours or less. Common Intermittent Fasting time frames are 16/8, 18/6, and 20/4. The x/x format means hours fasting/hours eating. For a 16/8 fast, that means 16 hours fasting and 8 hours eating. While 16/8 is the shortest amount of time recommended for an IF, you can create any length of IF by adding the fasting hours and eating hours together for a sum of 24 hours (16 + 8 = 24 hours, 23 + 1 = 24 hours, etc.).To apply IF to your lifestyle, you can count 16 hours (or however long you want to IF) ahead of your last meal. For example, if you finish dinner at 6pm, do not eat until the next day at 10am or later. This gives you 16 hours of fasting. You can then eat 1 - 3 meals from 10am until 6pm. Always eat till you are no longer hungry and never snack! Stop eating at 6pm and fast overnight again.
An EF is a fast longer than 24 hours. People in this group commonly plan fasts for 2 - 30 days and sometimes longer with doctor supervision! Most people can safely fast, but there are a few groups of people who should refrain from fasting: pregnant and breastfeeding women, children, people with certain medical conditions, people with eating disorders, after surgery or major illnesses, or anyone who is afraid of fasting. Read my blog post about who shouldn’t fast.
To prepare for an extended fast, research all you can on fasting to ensure you are safe and know the signs to break the fast and how to break it properly. Speak to a doctor about being monitored for fasts longer than 3 days. If you wish, start a LCHF (Low Carb, High Fat)/Keto diet 2 weeks prior to extended fasting to gain the most benefit from the fast as well as to make the fast easier to endure. Your body will switch to fat burning faster with dietary preparation. Many do just jump into an extended fast without preparing with the diet ahead of time.
Dr. Fung’s Recommended Fasting Schedules
Dr. Fung, the leading researching on fasting recommends a few different approaches to fasting depending on your goals and the time sensitivity of your need to lose weight.
The first recommendation is fasting for 24 hours daily. For example, you could eat dinner, fast 24 hours, then eat dinner the next day. This option is best for people who don’t need to lose a lot of weight or would rather take their time losing.
Fung’s second recommendation is to fast for 36 hours (1.5 days) three times a week. For example, you could stop eating after dinner on Sunday, fast through Monday, continue your fast through breakfast on Tuesday, and then eat lunch and dinner on Tuesday. The point is to skip four meals in a row with no snacking. After dinner on Tuesday, you would repeat the same schedule three times per week. This recommendation is for people who want to lose weight a big faster.
Fung’s third recommendation is to fast for 42 hours (a little less than 2 days) three times a week. Using the same example of stopping eating after dinner on Sunday, you would fast through Monday, continue your fast through breakfast AND lunch on Tuesday, and then eat dinner on Tuesday. For this recommendation, the point is to skip five meals in a row, again with no snacking and repeated three times per week. This recommendation is for people who should and need to bring fast weight loss results.
A 7-day water fast should only be repeated once a month, and a 14-day water fast should only be repeated once every 6 weeks. For the rest of the month, you can follow the 24, 36, or 42 hour plans above.
For people with extreme insulin resistance and who have Type 2 Diabetes, you should start out with a 7 to 14 day water fast (supervised by your doctor, especially if you are on medication).