Why do a three-day fast?

I’m not suggesting you should do an extended fast. In fact, I wouldn’t recommend it until you have:

  1. Become fat-adapted through at least four weeks of a low-carb, high-fat ketogenic diet, and
  2. Become comfortable with time-restricted feeding, with several weeks of maintaining fasting windows of 18-24 hours.

Doing #1 makes #2 much easier, but don’t rush it. Focus on eating your satisfying low-carb meals when you feel hungry, and start by avoiding post-dinner snacks.

Your goal is to achieve metabolic health, not to demonstrate willpower.

But once you feel established in a ketogenic eating pattern and have done some alternate-day fasting, extended fasts can create some impressive metabolic health benefits by unleashing autophagy.

Autophagy literally means “self-eating.” When nutrients are scarce, your body goes into this clean-up mode in which it digests and recycles cellular parts that are weak or defective, and replaces them with newly generated ones. See an excellent explanation of autophagy by one of my Health Sherpas, Dr. Jason Fung.

For a compelling overview of the benefits of autophagy, here’s a helpful video from another of my Sherpas, Dr. Sten Ekberg:

If you didn’t watch the video, the benefits Dr. Ekberg cited included:

  • Anti-aging – caloric restriction has been shown to improve lifespan, and many of these same benefits are thought to result from periodic extended fasting.
  • Detoxification as damaged proteins are recycled
  • Immune system enhancement
  • Improved tissue quality
  • Lowered insulin levels and increases in growth hormone
  • Reducing skin sag with weight loss, as the extra skin is broken down and recycled.
  • Brain-related benefits ranging from traumatic brain injury recovery to symptom improvement in Alzheimer’s and Parkinson’s diseases.

Even a relatively brief period of fasting triggers autophagy at some level, but to significantly activate it likely takes a couple of days or more. But unlike ketosis, which can be detected with a simple breath or finger-stick blood test, demonstrating autophagy requires a muscle biopsy.

Still, I think the framework Dr. Ekberg suggests is likely accurate: if you’re eating the Standard American Diet (SAD), you’ll likely take 72 hours or so for meaningful autophagy, but if you’re already fat-adapted it happens much sooner.

So I think given the eating pattern Lisa and I have been observing for more than a year, we’re likely getting a dose of autophagy with our 18-24 hour fasts.

One of the most compelling implications of autophagy is in cancer prevention, but no one really knows yet how large the dose needs to be.

This has been an topic of significant research interest and speculation that I will discuss in my next post.

If you think your friends might find this post helpful, I hope you’ll share by email or on your social networks using the buttons below.

To get these updates on a regular basis you can subscribe by email, or follow me on FacebookTwitter and LinkedIn, where I’ll also be posting links.

Check out My Health Journey for the full story of our health improvements, and my #BodyBabySteps for an approach to how I would do it if I were starting today, based on what I’ve learned.

Author: Lee Aase

Husband of one, father of six, grandfather of 15. Chancellor Emeritus, SMUG. Emeritus staff of Mayo Clinic. Founder of HELPcare and Administrator for HELPcare Clinic.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.