To drop weight means utilizing body fat for energy. That requires eating fewer calories. On keto Im much less hungry than eating SAD. So while Im not promoting 23/1 as better than any other IF window, my point is that intake must decrease lower than output such that the body must mobilize its fat stores to make up the difference.

For me, I cannot eat 24hrs worth of calories within one hour in other words, I will be full, but cannot eat some 2000 calories. This forces the stored fat to be used and weight will drop.

Initally calories in the form of ketones spill out thru the urine. But that is only for short period of time : as body becomes fat adapted, it uses those ketones as fuel.

Using stored fat is less efficient than just eating calories, so we get a little bumb in weight loss.

Ive heard some people dont switch back and forth easily. And sticking to very low carbs ( stay in ketosis) can be easier for most.