Here's the deal—we don't have lots of good data to support that intermittent fasting (IF) increases autophagy by a lot. Yes, IF increase autophagy. But for how long does that last?
On other hand, we have a crapload of studies on straight caloric restriction increasing autophagy. We don't have that with IF (Apart from studies in rats. Rats are not humans, though).
Next, at least some exercise is A LOT better than fasting for autophagy.
Lastly, here's what IF extremists forget to mention—if you fast for 16, 18, etc. hours, you may very well increase autophagy. But you also have a very short period of eating window during which you're heavily overconsuming food which, in turn, downregulates autophagy and downregulates protein regulatory pathway.
If you enjoy fasting and it fits your personal preference, crack on. But don't expect that it will be better for autophagy compared to regular straight caloric restriction. In fact, at this moment, we have stronger evidence that normal caloric restriction and exercise increases autophagy.