Our body requires a lot of energy to function properly. In this instance…Energy = 
Calories.
‘A moment on the hips is a lifetime on the hips’ is an old saying. This folk wisdom is not fiction, because calories are found in every possible food and drink (except water). When you ‘burn’ calories you expel energy. This is the natural way your body regulates a desired weight, however the foods available today contain way too many calories for our bodies to burn naturally. This is why many people are overweight. We must burn these excessive calories by increasing our amount of physical exercise
Exertion
The more you exert your body, the more energy you need, thus the more calories you burn. This means that someone who works out a lot and is very active needs more energy on average than someone who is rather lazy and tired.
According to international standard guidelines, men need 2500 calories a day and women need 2000. But these are just guidelines and not an established fact. For some people 1300 calories a day can be sufficient. Factors you need to consider when determining the amount of calories you need are height, weight, body type and how muscular (or not) you are. And what shouldn’t be forgotten is the level of activity. This isn’t just about working out; it is also about daily activities, such as taking the stairs instead of the elevator at work or going for a short walk during your lunch break.
Adjust your daily caloric intake to your lifestyle.
With this in mind, it shouldn’t come as a surprise that someone who is 6’7”often needs more calories than someone who is 5’3”, even when their activity levels are the same. A bodybuilder could easily use double the amount of calories of an average person. You could compare it to a car: a big, heavy engine uses up a lot more fuel than a small engine does.
You can use the Harris Benedict equation to find out what your recommended daily caloric intake is. Try out this calculator: http://www.mayoclinic.org/calorie-calculator/itt-20084939 this formula and much, much more information is available in our DVD ‘Healthy Weight Loss’.