The 6 Factors influencing your daily calorie needs
Your daily calorie requirements depend on six major factors. The formulas for
calorie calculations you are about to learn take into account all six of these factors to get
the most accurate estimate possible.
1) Basal Metabolic Rate (BMR)
BMR is the total number of calories your body burns for normal bodily functions,
including digestion, circulation, respiration, temperature regulation, cell construction, and
every other metabolic process in your body. In other words, your BMR is the sum total of
all the energy used for basic bodily functions, not including physical activity. BMR
usually accounts for the largest amount of your daily calorie expenditure - about twothirds.
BMR is at its lowest when you’re sleeping and you’re not digesting anything.
BMR can vary dramatically from person to person depending on genetic factors. You
probably know someone who can eat anything they want yet they never gain an ounce of
fat. This type of “fast metabolism” person has inherited a naturally high BMR.
2) Activity Level
Next to BMR, your activity level is the second most important factor in how many
calories you need every day. The more active you are, the more calories you burn; it’s that
simple. Become more active and you burn more calories. Sit on the couch all day long
and you hardly burn any.
3) Weight
Your total body weight and total body size are also major factors in the number of
calories you require. The bigger you are, the more calories you’ll require to move your
body.
4) Lean Body Mass (LBM)
Total body weight correlates with the number of calories you require, but separating your
total weight into its lean and fat components allows you to calculate your calorie needs
even more accurately. The higher your LBM, the higher your BMR will be. This is very
significant when you want to lose body fat because it means the more muscle you have,
the more calories you will burn at rest. Muscle is metabolically active tissue, and it
requires a great deal of energy to sustain it.
5) Age
Metabolic rate tends to slow down with age. Therefore, the number of calories the
average person requires also goes down with age. Fortunately, you can prevent and even
reverse the age-related slowdown in metabolism by developing more muscle through
weight training and nutrition.
6) Gender
Men usually require more calories than women. The average male has a maintenance
level of 2800 calories per day. The average female requires only 2000 calories per day to
maintain. The reason for this difference is not so much a sex-related issue as a body
weight and muscle mass issue; the average man carries much more muscle mass than the
average female and this explains the spread in calorie requirements between men and
women. Except for individual genetically-related differences in BMR, a 140 pound man
and a 140 pound woman would have the same calorie requirements if their activity levels
were identical.
Katch-McArdle formula (BMR based on lean body weight)
The Harris-Benedict equation has separate formulas for men and women because
men usually have a higher lean body mass and a larger bodies.
Since the Katch-McArdle formula accounts for LBM, this single formula applies
equally to both men and women and it is the most accurate method of determining your
daily calorie needs.
BMR (men and women) = 370 + (21.6 X lean mass in kg)
Example:
You are male
You weigh 172 lbs (78 kilos)
Your body fat percentage is 14% (24.1 lbs fat, 147.9 lbs lean)
Your lean mass is 147.9 lbs (67.2 kilos)
Your BMR = 370 + (21.6 X 67.2) = 1821 calories
To determine TDEE from BMR, you simply multiply BMR by the activity factor:
Continuing with the previous example:
Your BMR is 1821
Your activity level is moderately active (you work out 3-4 times per week)
Your activity factor is 1.55
Your TDEE = 1.55 X 1821 = 2822 calories
