I'm sure the idea of "calories in/calories out" is nothing new to anyone reading this. It's not so straightforward, however. In the case of burning excess calories, it is not simple math.
So, what's in a calorie? A calorie is a unit of energy that comes from food broken down by the body by a series of chemical reactions. These reactions supply energy for movement, warmth, metabolism, for breathing, among many other important bodily functions. It is commonly understood that a pound of body fat equals 3500 stored calories - in other words, fat.
Many popular diets would have you believe that if you cut back 500 calories per day for a week, you could lose one pound. Burn another 500 calories per day through exercise and that would equal another pound loss at the end of the week. In the same way, reversing the process would add on those 2 pounds. This may work sometimes but it doesn't happen that way consistently or long term.
If this process were as cut and dry as doing this...