What she said. If you have a smart phone, there are some terrific apps out there that will help you immensely ( if you use them ) It can be very educational and in some cases mind blowing to see how what you eat stacks up against your base nutritional needs and how exercise affects the whole equation. While approximate, an app like MyFitnessPal ( for pc or phone) can help you to determine your base calorie need for the weight you want to lose, and then help with the exercise portion. You can eat more when you exercise harder, but it has to be quality food, and it has to be within the range of what you "earned" by exercising, without going over.