The premise behind /r/leangains is working in a fasted state maximizes the gains for that workout.
This article covers some of the reasoning behind that belief:
https://leangains.com/intermittent-fasting-set-point-and-leptin/
no you dont burn more calories in fasted state. plus if you are fasted it doesnt mean you are in ketosis. to enter ketosis you need to not consume carbs for a much longer time than a day. train when you feel more comfortable