Versus nothing, and especially coming from a ketogenic diet, maybe a little. Having less stored carbohydrates in the body will likely reduce the time for a meaningful increase in autophagy by a few hours, but at 36 hours it’s still doubtful. There’s the whole sequence to go through - emptying the stomach, the small intestine, the ‘post absorptive’ phase where insulin declines and glucagon rises, depleting the stored glycogen, and the gradual increase and activation of AMPK while mTOR decreases and is suppressed (those last two are the most important regulators of autophagy).
If eating ketogenically beforehand, then insulin/glucagon should already be better versus a high-carb diet, and there likely will be less stored glycogen to deal with, but the overall picture isn’t much altered.
There isn’t a switch going from full Off to full On for increased autophagy. It’s a slow increasing curve, and at 36 hours maybe it’s rising a bit, but by far the largest gains are to come. Similar to people taking 3 or 4 days to really get into ketosis, I think the 3rd day or later is when we should look for substantial increases in autophagy. Nutrient deprivation is what does it, and the question is when has that really occurred enough.
There’s a shameful lack of human studies on this. The conditions for higher autophagy like insulin/glucagon keep getting more favorable past 5 days of fasting. If there is peak for it, we don’t know where it is. But for comparison, in a mouse autophagy is still increasing after 2 days of fasting, at which time the mouse is halfway or more to death from starvation. Nobody knows if there’s a proportional timeline in humans, but it would obviously be weeks/months for us.
Remarkable stuff happens during and after a fast. The one study I saw about human growth hormone had it peaking at day 26, I believe. Not saying that a given person should fast for that long, but for fasting in general there are beneficial changes that occur in the refeeding period after fasts of 3+ days.
We don’t know how great, in general, and especially on an individual basis. Autophagy does appear to be beneficial with some types of cancer - I’d say that’s the number 2 area. Number 1 is for dementia/Alzheimer’s disease/cognitive decline.
Autophagy is supposed to be going on in a minority of our cells, mostly a portion of our nervous system (where the cells are ‘post-mitotic,’ i.e. they can’t divide and make more of themselves). Since we’re stuck with those cells, some “house cleaning” needs to be going on all the time. The failure of this is thought to heavily contribute to dementia. Old, faulty, damaged protein structures accumulate in the cells and screw them up; this is the brain not working so well anymore. Autophagy scavenges these structures.
The individual needs to assess their own risk. Family history of dementia? People are living a long time now - what’s going to happen?
No death required!