I’ve read that intermittent fasting causes the body to enter ketosis in as little as 12 hours with a regular carbohydrate diet (so a typical intermittent fast schedule is 16 hrs of not eating and 8 hrs of eating). This is supposedly because the liver depletes its glycogen in about 12 hrs. But don’t muscles also store glycogen?
Furthermore, I’ve read elsewhere that it takes the body 2-4 days to enter ketosis when you eat a lower carbohydrate diet.
Can someone explain the distinction between these figures and how long it takes ketosis to happen?
In: 6
Yes. You have to eat less than 20g of carbs per day to get your body into ketosis in 2-4 days, then your fasting will work on your 16:8 schedule. If you want to stay in ketosis, keep your daily carb intake to only 20g. If you want to up it, exercise while you are fasting. Obviously, that’s a guideline and depends on age, activity level, and similar factors. Drink a lot of water, and you will feel when you are in ketosis with tiredness, constipation, and bad breath.
You enter ketosis when the sugar is burned. That’s it. Many people get into light keto every night, because you technically fast all night providing you aren’t a midnight snacker. If you have a liver full of stored sugar, ketosis can take longer. Exercise can get you there more quickly. To maintain ketosis, you need to ingest fewer carbs than you use. For many people, especially just starting out, 20g of carbs is the max and those are generally allocated to veggies for better nutrition.
As an aside, fasting is a tool for many things. One need not fast at all to get into and remain in ketosis. For some, it’s simply a way of managing eating.
It depends so much on:
– how much glycogen your particular liver and muscles has stored,
– how many (slow, undigested) carbs are still in your gut
– how much energy you expend.
Yes, muscles have glygogen but not as much as liver and they usually don’t release any sugar they make from it into the blood stream, unlike the liver, so the muscle glycogen won’t stop your blood sugar from dropping. So liver glycogen is what matters. If you don’t want to wait 12 hours for that to run down, do a couple of hours of sprint training. The energy for sprinting (unlike that for jogging) pretty much has to come from glucose. If you just walk or jog slowly, a fair proportion of the energy burnt will come from fat even if you aren’t “properly ketotic”. So if you are in a hurry to get ketotic, just keep doing 100 m dashes as fast as you can, one after the next as soon as you recover your breath. Keep doing this until you are fainting and voila, you have achieved ketosis in a matter of a few short but very gruelling hours 😉
(Not that I would actually recommend this, particularly the fainting while doing 100 m dashes bit. If you fall and hurt yourself, don’t blame me).
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