Yes - but it takes 18 to 36 hours for the contents of your stomach and liver to empty of stored energy based upon consumption and stores. After which time your body should be producing ketones, now your body needs another 24 to 36 hours to adopt to consuming its new fuel.
The best thing you could do is be super disciplined for four days straight, then you’ll feel the net result of your body being fueled by ketones. From your body’s perspective - Food cravings will be gone, energy will be balanced throughout the day, you won’t be hungry, your cloths will start fitting differently… now, from a phychological perspective, each time you feel hungry ask yourself if you are simply bored…