> It’s a physiological state that’s objectively quite hard to enter.
No, it isn't. The human body developed to bounce in and out of ketosis all the time. It's only hard to enter if you are always in a fed state and rarely in a fasted state. When you're fasting, it's not particularly hard to get back into ketosis in the same day, although it can take 24 to 48 hours for someone who isn't getting even light exercise. That's still way, way faster than the weeks it can take to get into ketosis on keto. (unless maybe you want to eat mostly protein and little fat, which is miserable)
I speak from extensive experience. A few weeks ago, after a 72 hour fast, I chowed on a pile of salmon sushi, measured my ketones throughout the day with ketone test strips, and was back in dark purple by the end of the night. Though normally it takes until the next morning for ketones to start showing up in my urine again, I believe it happened much faster because I was walking a lot that day. That was impossible to do back when I was just eating strict keto macros.
Anyone who doesn't believe me should try themselves by doing a few 72 hour fasts and refeeding on high protein, moderate carbs. They'd be surprised that it doesn't take an unreasonable amount of time to get back into ketosis. It's a perspective changer because it shows that occasionally eating carbs socially isn't the end of the world, because you'll be back in fat burning mode within a day or so.
So you can objectively track when your “bouncing” in and out of ketosis, like say for instance the way your heart beat changes ?
urine test strips only measure acetoacetate. Urinary ketones often correlate poorly with serum levels because of variability in excretion of ketones by the kidney, influence of hydration status, and renal function. (Wikipedia - I’m being a bit lazy).
I’m not arguing against fasting, or low carb diets. I’m making the point that ketosis isn’t as easy to “bounce” into as people think (though it doesn’t mean there are not benefits from fasting or low carb diets).
Your urine isn't going to show acetoacetate unless you're in ketosis. You're not supposed to use ketones to test accurate levels. It's to give you an idea of what's going on. There's no way your strips are going to show purple if your body isn't producing ketones for energy transport. The exact level doesn't even matter that much because what shows up in the urine is excess. Sure, acetoacetate is not the only ketone, but it doesn't just get created within the body for no reason. If you are fasted and you eat a bunch of ice cream, your ketone strip test will plummet to showing no signs of ketones at all. If you are fasted and you eat a fatty steak, at best you might see a slight decrease because of protein intake. This is consistent and easy to reproduce. I've repeated this test dozens of times. Carb and sugar heavy food plummets urine ketone levels and keto macros don't. Your body isn't going to produce an appreciable level of ketones when it's got simple carbs ready to go, which is because the body is going to prefer glucose every time it's given a choice.
And yes, you do bounce in and out of ketosis when you fast long enough, and it really doesn't take that long. Once you've expended your glycogen and you've digested all your food, your body doesn't have a choice but to dig in to fat stores. Depending on how much glycogen you have stored, what you've eaten, and how long it's been since you've eaten, getting into ketosis becomes ridiculously easy because the energy your body uses has to come from somewhere. You don't need to measure ketones to have confidence in this. It's well studied. If someone thinks that ketosis is hard to enter, I doubt they've gone more than a day without food. Once you get used to fasting for longer than 48 hours, it becomes obvious when your body is out of glycogen.
I suspect what the keto community calls "fat adapted" is basically that "easily bouncing in and out" state -- which some people reach easily, and some take weeks or months to achieve on keto. (but as far as I know, takes at most 3 days to achieve while fasting)
I am not sure if I have the correct understanding, so correct me if i am wrong.
Ketosis is not some magical mind state.
When all glucose and glycogen reserves are exhausted, body will start producing energy by burning fat reserves. To do so it needs to produce ketones. When low or glucose body will gradually start switching to ketosis to supplement energy needs and eventually fully switching to ketosis and only way of producing energy.
When glucose is available it will be used as primary 'fuel' source again.
That is a reason why after fasting its important to ease in the cards and sugars.
That's a reason, but likely not the only reason. There are likely reasons relating to regulation of other digestion processes that slow down to a halt while fasting.
Coming up from a fast and eating a lot of food quickly may cause refeeding syndrome - regardless of whether it is carbs or protein/fat.
Switching back to carbs from pure fat or pure protein is not dangerous in the same way, AFAIK (but I'm not a doctor).
No, it isn't. The human body developed to bounce in and out of ketosis all the time. It's only hard to enter if you are always in a fed state and rarely in a fasted state. When you're fasting, it's not particularly hard to get back into ketosis in the same day, although it can take 24 to 48 hours for someone who isn't getting even light exercise. That's still way, way faster than the weeks it can take to get into ketosis on keto. (unless maybe you want to eat mostly protein and little fat, which is miserable)
I speak from extensive experience. A few weeks ago, after a 72 hour fast, I chowed on a pile of salmon sushi, measured my ketones throughout the day with ketone test strips, and was back in dark purple by the end of the night. Though normally it takes until the next morning for ketones to start showing up in my urine again, I believe it happened much faster because I was walking a lot that day. That was impossible to do back when I was just eating strict keto macros.
Anyone who doesn't believe me should try themselves by doing a few 72 hour fasts and refeeding on high protein, moderate carbs. They'd be surprised that it doesn't take an unreasonable amount of time to get back into ketosis. It's a perspective changer because it shows that occasionally eating carbs socially isn't the end of the world, because you'll be back in fat burning mode within a day or so.