KetoFast Experiment

You should know by now that we like to try new bio-hacks, especially ones that incorporate fasting. From Intermittent fasting to traditional water-only fasts, we’ve tried them all. But one of the more intriguing things we’ve tried in the past year is the “fast mimicking diet (FMD)” popularized by Valter Longo in the Longevity Diet. We tried this last year and although we experienced good results and found it much easier than a a 5 day water-only fast (obviously), we just didn’t like his macronutrient suggestions. He suggests eating a plant based diet for the 5 day FMD period, and although there’s nothing wrong with that, the inherent macronutrient profile was far too carbohydrate rich for us, not to mention full of legumes and grains which we generally avoid.

We planned to repeat the experiment with a more Keto aligned macronutrient profile (high fat, moderate protein, low carb), but hadn’t got around to it until we stumbled on the the KetoFast approach, introduced by Dr. Joesph Mercola in KetoFast. The thrust of this book is that timing of meals matters almost as much as what you eat. He asserts (correctly) that humans spent most of our evolutionary history experiencing cycles of feast and famine, with famine being more common. Likewise, the idea of grazing constantly throughout the day and into the evening hours isn’t consistent with our ancestral health, where most eating occurred during the daylight hours. Plenty of research supports this notion that eating and circadian rhythm are deeply entwined.

After listening to Dr Mercola explain this way of eating on a recent episode of the Ultimate Heath Podcast, I realized that “KetoFasting” is exactly what we were looking for: Keto foods, fast mimicking framework, and circadian meal timing all rolled into one strategy. So we set out to try a week-long trial of KetoFasting adhering to these basic principles (you’ll have to read Mercola’s book or at least listen to his podcast to get more details):

• Time restricted eating: eat only during a 6 hour window from approximately 12 noon-6pm each day (he actually suggests doing this even earlier in the day, but 9am-3pm just isn’t workable for most)
• KetoFast day: eat only one small meal of 300-500 cal comprised of predominately fat and protein from collagen rich sources (rather than muscle meat) sometime between noon and 6pm
• Regular meal days: eat liberally with no caloric restriction, but still adhere to primal/paleo principles. Focus on organic vegetables, raw nuts, and pasture raised dairy/meats; Fruits and any other non-grain carbohydrates are allowed as well.

The results:

Since this is only a one week experiment thus far, these results are more about tolerability and immediate results, not long-term results. We structured our week with two keto fast days on Tuesday and Thursday; the remaining days were regular meal days but still adhering to the time restricted window. As somebody who has practiced time restricted eating for quite a while now this wasn’t too difficult because I’m used to skipping breakfast and eating my first meal close to noon but not having anything to eat after 6 o’clock was a little bit of a challenge, as I’ve grown accustomed to having a couple of squares of dark chocolate and maybe a glass of wine while unwinding in the evening.

The Ketofast days themselves were actually pretty easy: after all, eating 500 cal is a lot easier than eating nothing at all and I’ve done that for days on end. It was kind of a nice experience to break the fast with some high-quality macadamia nuts, bone broth, and avocado. It was only about 500 cal but felt like heaven. It really resets your expectation to eat constantly and makes you appreciate every bite.

After the first Ketofast day my blood ketone level was 0.7 mmol, while Rachel’s rose all the way to 2.0 mmol (consistent with prior experiments, she gets into deeper ketosis than I do). Hitting mild-moderate ketosis after 42 hours of eating only 300-500cal isn’t too surprising, but I was intrigued what would happen after eating “normally” on the third day. To my surprise, my ketones remained constant at 0.7mmol even after eating liberally and still I lost a few pounds to boot. Not to mention, I felt great throughout–excellent energy, mental clarity, focus, and very little hunger.

The second Ketofast day approached quicker than I would have liked. If we keep doing this Ketofast thing (spoiler alert: I think we will), I would probably only do it once a week, but would recommend more frequently to those needing to lose weight or change their health. For the second day I chose to eat the small ketofast meal at noon rather than in the evening. I strayed a little by eating muscle meat rather than pure collagen source as recommended.

By the end of the week my ketones were still at 0.9mmol and I lost 8lbs total in just 5 days. Now I’m sure a good bit of that is water weight, but nevertheless it’s pretty impressive. Despite the fasting schedule I kept my usual workout routine and felt that it did not impede my strength training days but did hamper my endurance a bit running full court basketball.

The verdict?

So what’s the verdict? Compared to water fasting or Valter Longo’s version of the fasting mimicking diet, the Ketofast approach was the best tolerated and most enjoyable. This may be due in part to the fact that it’s not a whole lot different from what I have been doing anyways, and I recognize that fact. But I effortlessly maintained moderate levels of ketosis for almost the entire five day stretch, never really felt hungry or “hangry”, slept well, exercised well, maintained excellent focus and energy throughout the day, lost 8 lbs, and truly felt that I got a great reset for my body and metabolism. I would highly recommend it to anyone looking to try a “supported fast,” and it will certainly be a part of my plan going forward.

~Brendan