The proposed diet - veg and fat - sounds like a form of keto. My experience with keto is that once your body is in ketosis, you also don't crave food; similar to fasting.
I would frequently be in ketosis before breaking fast per the urine strips - despite not intentionally limiting carbs at all.
It was an interesting experiment but after having a kid I found it tough to keep the routine. I was in amazing shape for a little while though