Being in a fasted state (zero calories) will help jumpstart the fat adaptation process. Doing this first thing in the AM will mean that you have not eaten for, maybe, 10-12 hour. This means that liver glycogen will be quite depleted. As muscle glycogen becomes deleted during the workout it will not be replenished from the liver so fat metabolism will be called upon to supply the needed ATP for the muscle work. Fasted means just that, fasted, no calories. Of course you do not have to adhere strictly to this method and if the workouts are long enough (varies depending on how fat adapted you are) you will still get some fat adaptation benefits. But fasted workouts will work best.
There is a ton of free info on fat adaptation on this site. Take a look at these articles: