Some people wonder how many calories they need to burn to lose a pound of weight. The answer can be found on Nutrition.gov .
Basically one of the answers it gives puts it at a reduction of 500 calories per day to lose 1 pound in a week. You can read more on their site along with many other helpful details on what happens when you eat more than what you need, how you can burn off stored body fat and more.
What I will say is that if you are trying to lose weight you may have to take up counting calories to get an idea of how much you are already taking in as opposed to how much you need to take in, or burn off, to lose the weight.
If you are trying to gain weight there is an answer for that too on the same page. Each answer seems to have links to where you can continue to study more.
If you are trying to maintain your weight in a healthy manner then the tips given for loss and gaining can help you decipher what you need to keep in your meals by way of calorie count and also how much working out you need to do to maintain instead of losing or gaining.