The Role of Intermittent Fasting in Ketosis – Part 1

Ketones are normally only made in quantity during a prolonged fast, as probably occurred a lot during evolution and even now possibly during illness or dieting to lose weight. Ketones are somewhat elevated even after a normal overnight fast.

– Dr. Charles Mobbs

I know I’ve probably already lost at least half of you just by bringing up fasting (the other “f” word), but stick with me here because it could be another instrumental piece to the proverbial puzzle in maximizing the benefits you get from ketosis. Periods of fasting cause the body to react as if it is starving, increasing the production of ketones.

But just mention the word fasting to someone on the street and the reaction you’ll get will probably fall somewhere between complete scorn to sheer terror at the idea of going without food for more than a few hours. Believe me, I understand, because I had the same reaction in 2006 when I first heard about intermittent fasting (IF) from a low-carb author, blogger, and physician named Dr. Michael Eades, author of the bestselling book Protein Power.

Dr. Eades wrote a blog post about IF that captured a lot of attention, generating the most comments that he had ever received on a blog post. The traditional method of fasting calls for alternating days of fasting and eating (eat Monday, fast Tuesday, eat Wednesday, fast Thursday, and so on). The IF plan that Dr. Eades was attempting, however, was a bit more practical. Here’s what his sample IF eating schedule looked like:

  • Day 1 – Eat anytime until 6:00 p.m. and then stop eating
  • Day 2 – Don’t eat until 6:00 p.m.
  • Day 3 – Eat anytime until 6:00 p.m. and then stop eating
  • Day 4 – Don’t eat until 6:00 p.m.

And so on. Of course, you aren’t constantly eating on the days you stop eating at 6:00 p.m.; you simply eat as you normally would, when you are hungry. And for the sake of his experiment with IF, Dr. Eades even said to feel free to eat whatever you want. However, he does advocate a low-carb diet and recommends sticking with low-carb foods while on IF to maximize its impact, especially for the purposes of weight loss.

Dr. Eades said it was very easy for him to skip breakfast and lunch. And if you think about what happens on the weekends, when your day is probably not quite as regimented as it may be on a hectic work or school day, you likely end up eating fewer meals almost naturally—even spontaneously. Still, I was extremely skeptical of the whole idea of fasting, even on an intermittent basis. Why would you put yourself through the torture of going without food, bringing on ravenous hunger, and fool yourself into believing you’ll enjoy it? Who in their right mind would ever do that?

That was then; this is now. The concept of fasting as part of a healthy lifestyle has become popular in recent years among people following a Paleo lifestyle (which hearkens back to the nutritional habits of our hunter-gatherer ancestors), many of whom are attempting to get into ketosis.

Intermittent fasting can be a powerful strategy for optimizing weight and health, but it is still highly controversial and misunderstood by many people. Who should be fasting and who should not? How long should you fast to get the most benefits out of it? Can you produce adequate ketone levels without fasting? These are just a few of the questions we’ll be answering in this chapter.

First, yes, it’s possible to have beneficial levels of ketones without fasting, but it can be difficult for some. If you’re eating the right amounts of carbs to your tolerance level, protein to your individual threshold, and fat to satiety and still aren’t producing enough ketones, it could be that you’re eating too much food, and perhaps too often, as we shared in chapter 10. Fasting will tend to bump up your ketone production.


The single largest problem for ketone production is excess calorie consumption. On the other hand, the ketogenic diet is therapeutic for a broad range of diseases when consumed in carefully measured and restricted amounts.

– Dr. Thomas Seyfried

When I started on my one-year nutritional ketosis experiment, I had no intention at all of fasting. But I quickly discovered that it just started happening spontaneously and naturally, especially when my blood ketone levels exceeded 1.0 millimolar. I remember early on, within the first few weeks of my experiment, my wife asked me when I last ate.

After looking at the clock and then going back through my food logs, I realized it had been about twenty-eight hours. I had totally forgotten to eat. If you know me well, then you’ll realize just how phenomenal this was! I was so satisfied by the ketones my body was producing that I couldn’t remember that I needed to eat something. Those days of being “hangry” were long gone, and I was now experiencing the power of ketosis in action.

I realize this all probably seems a bit odd to those who still think they need three square meals a day, as we all grew up believing. But it’s time to start looking outside the box of conventional wisdom and realize that fasting is probably a lot more normal than you think.

If you’re consuming a meal of whole foods that is low-carb, moderate-protein, and high-fat, with plenty of calories, then why would your body need to be fed again in just a few short hours? It wouldn’t. As long as you didn’t overdo it on the carbohydrates or protein and ate plenty of fat, you should be able to go twelve to twenty-four hours before your next meal rather easily.

Remember, this happens very naturally and shouldn’t be associated with any hunger or discomfort at all. Try it and see what happens. You may be tempted to cut back on the amount of food you consume when you eat more fat in your diet, but don’t. A meal should be pretty substantial, especially if it ends up being your only meal of the day.

Maybe that breakfast of two eggs and two slices of bacon should become four eggs cooked in butter and topped with cheddar cheese and sour cream, three slices of bacon, and an avocado. The former meal will likely have you looking for more food in a few hours, whereas the latter meal might take your mind off of food for the rest of the day. What freedom you can experience by making IF a part of your life!

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