Autophagy research is all over the place and its hard to understand this stuff or make blanket statements, instead we just have to be flexible with it. Autophagy is always working and the ramp up happens pretty quickly for a lot of people. I think aiming for the 48-72 hour peak isn't helpful. Most people cant or wont fast that long. A lot of people on 16-18 hour daily fasts see benefits that suggest autophagy working well.
Also biology isnt computers, its not exact and all our bodies are very different. For example, say your standing autophagy rate is 3. 16-18 hours fasting its 7 out of 10. But at 48 hours its 10. The difference between 7 and 10 might not even be very meaningful on a practical health level. The difference between never getting to 7 because of "it takes 48 hours" thinking and never trying is then huge. Just a couple hours a day at level 7 autophagy or whatever could be life changing. I do about 14-16 hours a day and am happy I made that decision for myself. I do see benefits that are real seeming to me.
From what I've seen there's no real downside to 14-18 hour daily fasting and in theory incredible benefits. Its also worth mentioning for a lot of people just sleeping with an empty belly means a higher quality of sleep, so there's secondary benefits as well. Your gut 'taking a break' during those hours may also be another benefit in terms of gut health as well, but I'm more skeptical of that claim.
Also biology isnt computers, its not exact and all our bodies are very different. For example, say your standing autophagy rate is 3. 16-18 hours fasting its 7 out of 10. But at 48 hours its 10. The difference between 7 and 10 might not even be very meaningful on a practical health level. The difference between never getting to 7 because of "it takes 48 hours" thinking and never trying is then huge. Just a couple hours a day at level 7 autophagy or whatever could be life changing. I do about 14-16 hours a day and am happy I made that decision for myself. I do see benefits that are real seeming to me.
From what I've seen there's no real downside to 14-18 hour daily fasting and in theory incredible benefits. Its also worth mentioning for a lot of people just sleeping with an empty belly means a higher quality of sleep, so there's secondary benefits as well. Your gut 'taking a break' during those hours may also be another benefit in terms of gut health as well, but I'm more skeptical of that claim.