You can also fast intelligently. Be careful about what you eat for your meals.
Eating pancakes, cold cereal, potato chips, or any high-carb meal will "crash" you in a couple of hours. At least it does this to me a lot. I avoid these kinds of foods on fast days.
Bread messes with your blood sugar more than if you had a bowl of sugar. Seriously, the glycemic index of bread is ridiculous. That means it takes your blood sugar on a wild roller coaster ride. It's worse than a can of coca-cola.
Go with foods that have protein, so you won't (blood sugar) crash.
Along with protein, look for foods high in FAT. Fat doesn't make you fat; quite the opposite. Grains and sugars -- carbs -- make you fat.
You find yogurt (milk intentionally soured with a bacteria culture) to be A-OK, but fresh milk to be "bad and gross"? Sorry, but I'm calling "stupid" on this one. You are inconsistent at best.
But as for the amount of food you eat, etc. that is left to each person, because each person has different caloric needs based on metabolism, what work you do, etc.