Recently there has been a renewed interest among health practitioners and the scientific community in the benefits and use cases for different types of fasting protocols. And it isn’t without reason.
Based on research, the are many benefits of fasting regularly or at some set period. Some people fast to lose weight, but the majority do it for other long term health benefits common to fasting. These include longevity, anti-aging effects, metabolic health, performance, and many others.
You’d think fasting is simple, however, there is actually a wide variety of different forms of fasting protocols practiced. So I wanted to break down the most common types to bring you guys some clarity. Some of these definitions will vary from mass opinion. Personally, I don’t believe this minutia matters much as long as you practice what works for you (fasting or not!) With that said, here’s a helpful guide.
Short Term Fasting Protocols
Intermittent Fasting (IF) or Time-Restricted Feeding (TRF)
The term Intermittent Fasting has become highly overused and often misused to mean all sorts of fasting protocols ranging from 36-hour fasts to daily caloric restrictions. What most people mean when they say Intermittent Fasting (or IF) however is the practice of Time-Restricted Feedings (TRF).
Time-Restricted Feeding (TRF) consists of limiting your eating window to certain hours of the day, most commonly by skipping breakfast. Common TRF protocols include:
- 16:8 – This is the traditional intermittent fasting method. It consists of fasting for 16 hours and eating during an 8-hour eating window. A similar method was actually originally pioneered by a bodybuilder for the popular LeanGains method.
- 18:6 – Similar protocol to the 16:8, however, instead of 8 hours, your eating window is 6 hours. Similarly, you fast for 18 hours on this plan.
- 20:4 – Following the same logic, practitioners have a 4-hour eating window every day. In 2001 Ori Hofmekler published the book “The Warrior Diet” which essentially created the 20:4 protocol.
- One Meal A Day (OMAD) diet is literally what it says. As you can imagine, it closely resembles the Warrior Diet above.
Other Short Term Fasting Protocols
These next dieting protocols also belong to the short term fasting group:
- A 24-hour fast is basically fasting for 24 hours. You can pick when to start the fast and then end it exactly 24 hours later. This is done typically at either a weekly, monthly, or quarterly frequency. Though there certainly is no hard and fast rule.
- A 36-hour fast, consequently, involves a 36-hour fasting window. It’s common to start fasting after dinner of day one and end the fast on the morning of the third day.
- A 5:2 fast is another form of intermittent fasting that consists of 5 regular eating days and 2 non-consecutive fasting days. On the fasting days, practitioners may limit intake to 25% of normal consumption (or 500 calories) instead of a complete fast.
- Alternate Day Fast is when you fast on day one and then eat normally the next day. This pattern continues for as long as you wish. Some also call this the Stop-Eat-Stop method.
Extended Fasting / Prolonged Fasting
Prolonged or extended fasting involves fasting for more than 36 hours. There is no particular reason other than this is about when you start to run glycogen stores dry and your body starts to activate alternate metabolic pathways.
A common length is either 3 days, 5 days, or a week. Although there are a number of people who have successfully undertaken fasts lasting up to 40 days. George Cahill conducted a fascinating experiment looking at long term starvation {*}.
Many people who practice extended fasting, do so for medical reasons. Certainly, weight loss is another benefit. However, any time you undertake a fast diet, especially one that requires missing meals for more than 5 consecutive days, you want to be very conscious of how you break your fast and minimize any muscle loss.
Fasting-Mimicking Diet (FMD)
Dr. Valter Longo created the Fasting-Mimicking Diet in partnership with a company called ProLon. The diet plan consists of a 5-day fast that includes a limited number of calories with a specific macro and micronutrient profile. On the first day, you are allowed to consume up to 1000 calories, while the next 4 days top out at around 700 calories each. There are several types of similar diets available to purchase online. Alternatively, you can actually create your own FMD plan. Just search any number of the available guides out there or buy the book by the same name.
The FMD diet claims to provide nearly the same benefits as a 5-day water-only fast, while admittedly being much easier to stick to. And since the discomfort of skipping meals for a week is the number one reason people are hesitant to try these protocols, the FMD diet seems like a wonderful compromise.
More Fasting Resources:
XO, Marina
Disclaimer: I am not a medical doctor or Registered Dietitian. The information presented is not medical advice. It is purely to share my experiences and opinions based on the linked research. As always, check with a doctor before making any fitness or nutrition changes. The author and blog disclaim liability for any damage, mishap, or injury that may occur from engaging in any activities or ideas from this site.
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