Some of the problems many people face when they count calories or set a number of calories to take in...is they end up not taking enough calories and their body goes into starvation-survival mode and your metabolism slows down. Please understand that you need enough calories to power you through your workouts. Calories give you the energy to exercise with intensity. It is mostly true that a calorie is a calorie-the difference between eating 1,500 calories of Oreos and eating 1,500 calories of chicken is fairly minimal in terms of actual weight gain. So the most important thing to think about in regards to calories is that leaner bodies need more calories than less lean ones.
Zinczenko, David. Eat Right Every Time Guide. Pg. 61.
Michaels, Jillian. Making The Cut. Pg. 10, 12.