Men usually have less body fat and more muscle than do women of the same age and weight, which means men burn more calories. Your age. As you get older, the amount of muscle tends to decrease and fat accounts for more of your weight, slowing down calorie burning.
Calorie needs peak at about age 25 and then decline by about 2 percent every 10 years. So if you’re 25 years old and need 2,200 calories to maintain your weight, you’ll need only 2,156 by the time you’re 35; 2,113 at age 45; 2,071 at age 55; and so on.
A living body needs a minimum number of calories to maintain vital functions, such as breathing and keeping its heart beating. This minimum number is called Basal Metabolic Rate (BMR).
Your body shape and size affect the number of calories you need because muscle burns more calories than body fat does. So if you’re solid and have a greater proportion of muscle to fat, your metabolism is higher. Likewise, if you have more body fat and less muscle, your metabolism is lower, and you have a greater tendency to store fat than someone who is tall and thin.
