“How many calories do I burn in a day?” If you are looking at altering body composition – whether you are looking at putting on muscle mass or a looking to burn body fat, this is a key question you should be asking yourself.
Your basal metabolic rate (BMR) is the amount of energy you expend in carrying out your everyday basic bodily functions. The expenditure of energy in this situation is only the amount required for physical survival through the continuing function of your vital organs.
The factors that determine your basal metabolic rate are:
To determine what your basal metabolic rate is, you can use the following Harris Benedict equations. Here are two sets of equations to suit whether you use imperial or metric measurements:
Imperial BMR Equation
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) – ( 6.8 x age in year )
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) – ( 4.7 x age in years )
Metric BMR Equation
Men: BMR = 66 + ( 13.7 x weight in kilos ) + ( 5 x height in cm ) – ( 6.8 x age in years )
Women: BMR = 655 + ( 9.6 x weight in kilos ) + ( 1.8 x height in cm ) – ( 4.7 x age in years )
Of course, this gives us only the basic caloric use for mere survival and doesn’t take into account lifestyle factors that determine your total daily energy expenditure (TDEE). A 180lb, 5’ 7”, 35 year old man, who leads a sedentary life and does not exercise, burns far less calories than a man who lifts seriously 4 times a week and has a solid conditioning routine.
This means you have to multiply your BMR by your level of activity:
TDEE = BMR x Activity Level
- If you are sedentary: TDEE = BMR x 1.2
- If you are lightly active (light exercise 1-3 days a week) : TDEE = BMR x 1.375
- If you are moderately active (moderate exercise 3-5 days/week) : TDEE = BMR x 1.55
- If you are very active (hard exercise 6-7 days a week) : TDEE = BMR x 1.725
- If you are extra active (very hard exercise & physical lifestyle) : TDEE = BMR x 1.9
So to use the previous example of two 180lb, 5’ 7”, 35 year old men, their BMR would be 1800 calories (rounded to the nearest number). However if one man had a sedentary life, utilising his spare time watching television and the second man worked out moderately 4 times a week the TDEE would be significantly different.
- The first sedentary man’s TDEE would be 2160 calories.
- The second moderately active man’s TDEE would be 2790 calories.
This is the total amount of calories burned according to the amount of activity we engage in
This is a very important number.
If we keep the activity levels the same and ate an equal amount of calories as our TDEE our weight would be maintained.
If we ate less calories, without altering our activity level, we would lose a moderate amount of weight over time. If we ate more our weight would increase over time
Now imagine, using this base number, eating 20% less calories and increasing our activity factor by adding cardiovascular work. Our caloric deficit increases.
Now imagine adding some serious resistance training, that keeps our metabolism ramped up for longer periods of time. Then if we manipulate our food intake, at the macronutrient level, by changing the ratio between protein, fats and carbohydrates and manipulate the times we eat our food, steady fat loss is assured.
The same sort of factors apply when we want to increase lean muscle mass.
We can increase our caloric intake, lessen cardiovascular work, increase rest periods, increase our level of resistance training (less volume, more poundage) and manipulate our macronutrient ratios.
So you see working out your BMR and TDEE numbers gives you a caloric baseline to work from.
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