Why I settled on Three Days for Cancer-Prevention Fasts

Intermittent fasting and time-restricted eating have been a huge part of my health journey and of Lisa’s, thanks to an introduction to the concept from Dr. Jason Fung.

When we tried 10 weeks of alternate-daily fasting, that was when Lisa really started to see impressive weight-loss results.

Now fasting is just part of our routine. As I’ve tracked with the Zero app, I have fasted at least 13 hours on 269 of the last 270 days.

Usually I have two meals a day, four to eight hours apart. Sometimes it’s just a single meal, a.k.a. One Meal A Day or OMAD, which is what Lisa typically does.

Occasionally we fast for more than 24 hours to accelerate autophagy and for cancer prevention.

I believe I first heard of the idea of fasting for cancer prevention through Dr. Fung, primarily in the context of how long-term caloric restriction has been demonstrated to increase longevity and to reduce cancer incidence, both in animals and in people.

But who wants to live like that all the time?

What if you can get most of the benefits of chronic restriction through periodic pulses of fasting, while eating normally the rest of the time?

That leaves the question of dosage: how long does the fast need to be, and how frequently do you need to do it?

The short answer is no one really knows, but here is why Lisa and I have settled on three days once a month.

I had heard about Dr. Peter Attia’s practice of a seven-day water-only fast (a.k.a. the Nothingburger) once per quarter as a potential cancer-prevention strategy, and so I decided to try a seriously extended fast for the first time about 15 months ago.

Instead of water only I also allowed myself coffee, and I went five days, from Sunday evening to Friday evening. I did another of these last February, but cut it to four days because my sleep quality the previous night hadn’t been good.

Meanwhile I heard that Dr. Attia had changed his personal practice to a three-day fast each month. It’s two more days of fasting per quarter, but spread out over three months instead of all at once.

As I said, no one knows the “right” dose and frequency, but this seemed like something worth trying.

In November and December I did three-day fasts. The slightly lower intensity than my previous 4-5 day fasts was appealing, but I still had that nagging question of whether it was enough.

Then I finally checked out some videos from Professor Thomas Seyfried (as highlighted in my last post) on the metabolic approach to cancer treatment through a ketogenic diet and related interventions.

He described the glucose-ketone index (GKI) he had developed to measure whether patients were in an optimal, deep level of ketosis. A GKI of 9.0 or less indicates some level of ketosis, with 1.0 or lower being the highest therapeutic level.

Increasing ketones and reducing glucose allows normal cells to thrive, while cancer cells – which lack the ability to use ketones for energy – are placed under stress.

I also was interested in confirming that my normal blood sugar levels weren’t masking an underlying condition called insulin resistance. If I had normal blood sugar levels only because my pancreas was cranking out lots of insulin, that would not be healthy.

I felt pretty confident that I had reversed any insulin resistance I may have had before my weight loss, but I wanted to confirm it.

Testing insulin levels is complicated and expensive, but I had learned that having ketone readings of 0.5 mmol/L or higher is a back-door way of confirming low insulin levels. They’re in a reciprocal relationship: elevated ketones aren’t compatible with high insulin.

I also heard someone mention the Keto-Mojo device that enables home measurement of blood glucose and ketones, and which enables tracking through a mobile app, so I took the plunge and got a starter kit for about $100.

My Keto-Mojo arrived the day after I started my December fast, and that evening my GKI was 3.2. By the 48-hour mark of my fast I reached 1.0 and I stayed below that (0.8, 0.5 and 0.5) until I broke my fast 24 hours later. I remained below 3.0, which is considered high-level ketosis, for another 24 hours. I maxed out at 6.2 mmol ketones with blood sugar at 61 mg/dL.

It seems that if GKI at or below 1.0 is the therapeutic target for those undergoing metabolic cancer treatment, being there for at least 24 hours once a month gives a reasonable chance of being helpful in cancer prevention.

It isn’t rock-solid confirmation for the three-day fast Dr. Attia uses, but it gives me some reason to believe I’m in a fasting range that should be beneficial.

I think Professor Seyfried put it well toward the end of the video I embedded in my last post:

These are non-toxic approaches. I can’t tell you whether it’s going to be the solution to the cancer problem. But I can tell you ‘I think it works, and it’s not going to hurt you. And it has the potential mechanistically to be very effective.'”

Thomas Seyfried, Ph.D.

Our next three-day fast starts tomorrow afternoon. This time I’ll be working to ensure I’m in ketosis before I start my fast, which should make it easier, and also will be taking GKI readings throughout the full fast instead of starting partway through the fast.

I’ll also explore strategies to get to that GKI ≤ 1.0 as quickly as possible to have the greatest therapeutic effect.

I’m not asking you to join Lisa and me in this fast, but if you’re curious I do invite you to follow along as I share observations on Facebook, Twitter and LinkedIn.

I’ll also write a daily recap post here that you can receive if you subscribe by email.

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.

The Fast after the Feast

Some people I respect recommend doing an extended fast before holiday feasts. Dr. Peter Attia, one of my Health Sherpas and the medical director for the Zero fasting app, often leads a group fast before Thanksgiving and Christmas.

This is a good approach because it allows you to enjoy holiday feasts guilt-free: you’ve already paid your dues.

For Lisa and me, with our wedding anniversary on Dec. 22, that’s not such a good option. We did our feasting from then through Dec. 26, and I began my extended fast at 5:30 p.m. on Sunday, Dec. 27.

During our feasting period, I had gained 7.4 pounds. And to be candid, I had already crept up a couple of pounds in the first half of the month. So by the day after Christmas I was 10 pounds heavier than my November average.

Clearly this was a lot of water weight based on my high carbohydrate intake. I also felt more stiff, with some carb-based inflammation.

The goal of my fast was to burn through that carb excess quickly to get into fat-burning mode, and so to jump-start the process I began early Monday morning with a high-intensity interval training workout, as Dr. Attia advises.

My Tuesday workout included free weights and a zone 2 cardio workout. This lower-intensity training is at the maximum level of exertion that can be sustained without burning glucose. That’s both necessary, because glycogen stores are depleted by the second day of a fast, and desirable, because it improves the muscles’ ability to burn fat.

Wednesday I did another zone 2 workout for the same reasons.

I had set on my Zero app timer goal at 36 hours, but my real goal was a three-day fast. I wanted to be able to declare victory early in case I wasn’t feeling well. I was able to finish strong, however, and had my fastbreaker just after 6 p.m. Wednesday.

It’s important to not overeat coming out of an extended fast of more than 48 hours, and particularly to not overdo carbs, which cause you to retain water and can throw your electrolytes out of balance.

My keto-friendly first meal is below, although I’ll confess that I did go back for one more stuffed pepper. The graph at right shows results of my morning weigh-ins for December and into today, which was my 300th consecutive day using our Bluetooth scale.

Why the 2.6-pound bump at the end? Last night was New Year’s Eve.

I guess I feasted before and after the fast.

I’ve done several of these longer fasts in the last year. One was five days and another four, and my plan going forward is to do a three-day water-only (or water and black coffee) fast once a month.

I’ll discuss reasons behind this in my next post, along with some interesting findings from the glucose/ketone meter I used for the first time this week.

If you haven’t tried fasting or time-restricted eating, you can take a great first step toward improving your health and vitality as we start 2021 by just not eating in the evenings.

I’m not suggesting some grand New Year’s Resolution that sets you up for failure. Just some #BodyBabySteps.

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Getting Started with a Satiety Sandwich

When Dr. Peter Attia, one of my top Health Sherpas, is about to go into an extended fast, such as a three-day or seven-day water-only fast, he has found that a week of nutritional ketosis on either side of the fast makes it much easier.

He calls it a Nothingburger: the “meat” in the middle (the fast) is literally nothing, and it’s sandwiched between two slices of ketosis. Being in ketosis when starting a fast means his body is already using ketones because he has been consuming high levels of fat, very few carbs and a modest amount of protein.

So when he switches to fasting (the “nothing” part of the burger), he’s already in fat-burning mode, and his body smoothly moves from using the fats he’s been eating to using his stored body fat.

No wild fluctuations in blood sugar. No carb cravings. And when breaks his fast, he resumes his ketogenic diet, which helps prevent refeeding syndrome.

You can accomplish a lot metabolically without engaging in these longer fasts. We’ll discuss fasting and time-restricted eating in #BodyBabyStep Four.

But for now, as you’re getting started in your body makeover, another gastronomical metaphor will be more helpful.

Nothingburger vs. Satiety Sandwich

It’s helpful to think of the first three #BodyBabySteps as a Satiety Sandwich, but unlike the Nothingburger you “eat” them all at once.

All three are essential. Without stopping sugar and cutting carbs, your insulin will stay high and won’t lose weight. And if you don’t embrace filling dietary fats, your hunger hormones will eventually wear down your willpower, and you’ll overeat the carbs.

Filling fats from healthy natural sources such as beef, poultry, fish, dairy, eggs, olive oil, avocados and nuts will help you feel satisfied so you can resist the sugar and carbohydrate cravings.

So unlike Dave Ramsey’s financial baby steps or the three stages of the Nothingburger, you don’t take the first three #BodyBabySteps one at a time.

They’re a delicious and satisfying package. With filling fats you can drive the sugar and carbs toward Nothing.

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“What if we’re wrong about diabetes?”

That’s the title of this video, which came up in Lisa’s YouTube related videos feed about a year ago.

It’s a gripping TEDMED talk from 2013 by Dr. Peter Attia, who confesses the judgmental attitude he had harbored six years earlier toward an obese patient who had come into the emergency department with foot ulcerations.

She obviously must have let herself go, he thought, consuming too many calories and not moving enough.

But then three years later he found himself 40 lbs. overweight and with metabolic syndrome, and he knew that physical inactivity was not the cause in his case: he had been “exercising three to four hours every day, and following the food pyramid to the letter.”

It led him to wonder whether, in the case of obesity, insulin resistance and type 2 diabetes, the medical community might have the chain of causation backwards.

Watch this video. It’s totally worth the 16 minutes.

I have found Dr. Attia one of the most thoughtful online voices when it comes to evaluating and making sense of dietary and lifestyle research related to both longevity and healthspan.

As he says in this video, perhaps he’s been humbled by what the thought he knew that turned out to be mistaken.

I expect I will have several more posts in this series that feature (or at least mention) Dr. Attia. His website is an amazing resource, and his podcast, The Drive, is the only one for which I pay for premium access.

Like Tim Ferriss, Dr. Attia also has introduced me to many other leading researchers and thoughtful analysts. Follow him on Twitter.

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