It’s not that vital if your eating window/carbs are constricted. A lot of people do rolling fasts where they fast for 48+ hours and only eat 1 meal before fasting for 48+ hours again. If you eat throughout the day you might struggle because your body will have insulin so it won’t ingest your fat as readily and you’ll feel sluggish.
If you want more calories - bulletproof coffee is a popular keto thing (I think it’s gross personally but to each their own).
If you are not getting a lot food though you need to really make sure that you’re getting enough electrolytes.
Also you could try eating fattier meats - I love rotisserie chicken with the skin on my feeds some times for a low cost higher calorie meat.