A calorie is a unit of energy. Our bodies require a certain number of calories on a daily basis in order to perform normal daily functions from moving around, to digesting, to rebuilding cells and tissues. We fulfill our energy needs through the food and beverages we consume.
The calories you require on a daily basis depend on a set of unique individual factors:
Age. During periods of growth, like infancy, youth and pregnancy, the body requires more energy and nutrients—especially protein which is used to build growing tissue. As we get older our caloric requirements generally decrease since muscle mass has generally decreased and tissue growth has declined.
Gender. Males typically have higher caloric requirements because they tend to biologically have a greater muscle mass than women. In general, the more muscle you have the more energy you burn and therefore require.
Body size and composition.Typically, larger bodies or ones with greater muscle mass will burn more and thus require more energy (calories).
Physical activity. Physical activity is a form of energy expenditure and will increase energy requirements the longer and more intense the activity it is.
Basal Metabolic Rate. This is the energy your body expends at rest, (during sleep) for basic functions, such as breathing, circulating blood, adjusting hormone levels, and growing and repairing cells. This typically accounts for about 60 to 75 percent of the calories you burn every day (believe it or not!).
Trauma, injury or health condition. During times of trauma or injury the body burns extra calories because it is constantly trying to repair damaged tissue. Certain diseases or conditions like a metastasized cancer can also require more energy (and protein) than what a healthy body would require.
There are ways to estimate your caloric needs for the day, although the estimate will be exactly that—an estimate. It can give you an idea of the calories your body requires on a daily basis. Meals and snack choices can then be planned accordingly in order to lose, gain or maintain your weight.
Do you know how many calories you need on a daily basis? Check out Mayo Clinic’s interactive calorie calculator here.
The estimate given will be the calories your body requires to maintain your current weight. To lose at least a pound a week, 500 calories will need to be deduced every day. This can be done through diet alone, though it is recommended that physical activity be incorporated as well. (Note: 500 kcal x 7 days = 3500 kcal = 1lb/week.)