I'm not convinced fasting is the way to go. I calorie count on a daily basis. I know what my base "maintenance" calorific intake should be. That is what I need for a normal, no exercise day. For example I know as I write I have 166 cals left for the day - this includes what I've already logged for my dinner as it's prepared.
If you decide to calorie count do this by testing yourself not from some algorithm or other. Log your food intake for a week, then reduce weekly by 200 cals until you reach the week when you're hungry all the time. You're now below your daily needs, add 200 cal to the total and off you go. I usually feel hungry 30-45 minutes before meal time.
I use My Fitness Pal which comes in both free and paid versions. I find the free version more than adequate. It's very simple to use and a handy bonus is it can auto-connect to Strava, download your exercise for the day and add these calories to your daily total.
I'm a strong advocate of "fueling exercise." The basis is when exercise is planned one should take in additional calories to "fuel the ride." If one rides without fuel the body becomes stressed, uses its reserves to fuel the exercise and, crucially, will learn to react to this stress by storing calories as a defence against future stress. Those calories are stored as fat.
Keep in mind often when we feel hungry we're actually thirsty. Adequate hydration is very important. My base water intake is 2½ litres per day, more when I ride.
