I have been doing IF now for almost 2 years. I researched Keto to no end and attempted it only to be stopped by heart issues (pre-existing). I still IF with only a 2 hour eating window at night out of sheer convenience and some of the other obvious benefits like autophagy, improved insulin sensitivity, etc.
All the reading and research I have done states that ketosis does not start happening until about the 3rd day+ for most people as they have to deplete their glycogen, liver, etc before the body will start burning fat / fat stores. To further that most reading I have done says it takes months to become extremely fat adapted. Maybe all that previous information is false making this question pointless but here is my question:
What benefit do my 22 hour fasts or even for that matter 2 day fasts have on my body in terms of burning fat when it takes the body longer then that to start using existing fat stores or incoming fat via food intake?
Your body is always making ketones. Even carb eaters make some ketones to get them through the nite. But you are right, the bulk of your brain’s conversion to ketones occurs in days three and four at the <20 net carb intake level with adequate protein at a reasonable deficit. Keto works because it mimics a fast. Fasting works because it is a fast. All the same effects that you read about on keto will happen with full fasting, just a bit faster.
If you eat a ketogenic diet at a calorie deficit, you will lose body fat. If you fast, you will lose body fat.
If you do a full fast for a day or two when coming from a high carb diet, it has an effect on insulin sensitivity, even if you don’t burn through all your glycogen stores or become keto-adapted. If you do a full fast for a day or two when coming from a keto diet, I will attest that it is much easier to handle.
I don’t have an exact answer for you except to say if you aren’t varying the length of your IF, your body has probably adjusted to your routine. Dr Fung suggests 24-48 hour fast upto 7 days. Everyone responds differently.
>What benefit do my 22 hour fasts or even for that matter 2 day fasts have on my body
Increasing Insulin sensitivity for one. Not to mention giving your body a break from blood glucose spikes and insulin surges.
Also, there is autophagy which doesn’t go to 11 like when you fast for several days in a row, but probably still has a good, if milder, effect. If you are regularly eating 22/2, then the benefit accumulates.
Also, don’t worry about not burning fat. You are using your fat stores. The amount of glycogen in your body is just not enough to prevent that, plus if you don’t refeed with heavy carb, or do some intense exercise, your glycogen will always be depleted and you body will have to make it’s own glucose from your fat stores in order to replenish it. IOW, don’t worry, you are losing fat.