Whats the best and least time consuming way to burn body fat?

The best time to eat: morning, lunch (here you can eat quite many, much more than other time), dinner.

Make it normal 3 times eating schedule daily, the point is eat much more at lunch but don't eat until you feel full (example, eat 1 bread at morning but at lunch you can eat 2 bread).

At dinner and morning eat, don't eat too much. For 6 pack, your food must be low fat and low calories foods. Avoid fried, butter, salt, additional spicy/taste for food, mayo, and other similar on those line.

Then add cardio (4-6 times in a week) + sit ups training (i think you already do it / knew it), hopefully you can build it faster.

Additional, for cardio, you can do swimming and or walk a little fast for 1 hour or more. So it's not always running.

Try kickboxing. It is amazing cardio that burns fat very quickly. You can find videos online or buy some kick boxing DVDs. If you have the money and desire, you can take classes.

start doing some cardio, go on an incline if you can will help burn more calories and keep an eye on the diet