Multiday fasting is 2-3 days of continuous fasting or longer.
Our bodies are remarkably good at remembering our behavior and will actually trigger detectable and undetectable events to make sure it gives us what we “tell it” we need.
For example, I had a pattern of fasting Wed-Thurs-Fri every week… then I switched it and decided to fast Mon-Tue-Wed instead. For those three fasting days, my glucose was much lower and my ketones were also lower than usual. This was because I was fasting when it was expecting food. Then when I ate while it thought I’d be fasting, my glucose and ketones went much higher. The ketones were high because it expected me to fast and my glucose was high because the food spiked it when it wasn’t prepared.
This isn’t just about eating. This Saturday, I did some intense lifting (usually I reserve the weekends for rest) and that exercise dropped my ketones from 0.7 to 0.1 … I consumed ketones faster than my body was prepared to deliver new. My glucose likewise dropped. Then on Sunday, at the same time as my exercise the previous day, my ketones skyrocketed for no reason at all. They went from 0.7 to 1.7! I was literally sitting down watching videos and my body “remembered” that this is when I tasked it to lift the day before and was “prepping”… not wanting to be caught unprepared…
That’s been my experience. We have amazing bodies and they are trying to keep us alive and healthy. Even the hunger signals are an attempt to communicate what it thinks we need based on a massive library of events we’ve experienced.
I’m an old timer now and a geek but I used to love the “knight rider” show with the smart car “kit” working with the star Michael (Hasselhoff) to solve crimes. It didn’t just obey. It tried to help by predicting, analyzing, remembering and even arguing with the human who was “in control”. They were real partners and better because of it.
I know I sound like I’m in conflict with my body but I’m really not. It’s a partnership but my body can’t speak to me directly. It’s like a super-smart amazing machine and friend who watches everything I do and is tasked with keeping me healthy and alive. I behaved badly for decades and it remembers. Now I try to listen to it more and understand its motivations better.
I call it “lazy” or “greedy” sometimes because it wants to eat and rest. But I taught it that that’s what I want. It’s working to economize energy usage because that’s what it was programmed to do and it’s what I reinforced for decades. Now, we’re reprogramming the source code to want different things and it’s working… slowly.
My predicted resting metabolic rate (RMR) is 1700 cal/day based on age/height/weight but my measured is 2700 cal/day. That difference is because my body knows that I want to use that energy and I want to use it now. It knows that I will ignore hunger signaling and that I take it as a signal to go for a walk, so now I get hunger signals coinciding with higher ketones …
Mind-body communication is a new frontier for me, but I’m liking my new discovered friend.