I did kept meals while fasting and weight just melted off if that is what your goal is. I did 30g or less a day with a lot of protein, leafy greens and I used avocado, cheese and butter in my cooking to get fat content
If you’re actually in ketosis, yes. Sometimes the fasting apps say you are after so many hours, and often that’s true… but sometimes it’s not. And depending on a person’s diet, when they refeed, they’re definitely not going to stay in ketosis. But if you typically eat low-carb (<50ish g a day) or ketogenic (<20ish g a day), are in ketosis from fasting, then eat a low-carb meal? I would say yes.