Your body needs energy to function. It may surprise you, but there is a beehive of activity going on even when you are not doing much; just sleeping for example. Even this simple act of sleeping requires energy as your body keeps your liver, kidney, heart, brain and the rest of you functioning. The amount of energy required for you to claim existence is known as your Basal Metabolic Rate or BMR. Your BMR is the minimum amount of energy that your body needs to function at rest expressed in calorie terms.
Using the fundamental laws of physics, your BMR is a function of your size or mass. Say you are a tall building size; you would need a lot of energy to survive. If you are a small bungalow size; the energy required would be lower. Your age and gender also come into play as your metabolism is geared toward the unique role that we play in humanity.
Various scientists have attempted to calculate or determine the appropriate formula for BMR. Perhaps, the best recognised is the Migglin St. Jeor Equation for men and women.
The equation for men is 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5
The equation for women is is 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years)- 161
The formula makes it clear that women require a slightly lower amount of calories per day as compared to men. Also, as you age, your muscle mass declines by approximately ten percent after the age of thirty, every decade. The decline means that your metabolism and therefore your BMR is also falling. The fall in metabolism, captured in the formula, implies that you need to cut back on your eating as you age.
The minimum calorie intake required for a human being is your BMR x 1.2 (little or no exercise) and up to BMR x 1.9 for heavy exercise (twice per day extra workouts). For most of us who may be engaging in moderate exercise 3-5 times a week, your minimum intake is BMR x 1.55.