Understanding the Basal Metabolic Rate : BMR

The basal metabolic rate (BMR) is the amount of energy, in terms of the number of calories that the body burns at rest just to maintain normal body functions such as breathing, circulation, digestion, etc.

This is the minimum number of calories that you require to go through your day. If you consume the BMR amount of calories, be idle throughout the day, you will not be dipping into your fat reserves for energy. If you eat less than the BMR and be idle, some fat from your body will be used to meet the shortfall. Now, if you throw in some light exercise for more than 45 minutes, like walking for an hour (around 175-200 calories expense), and eat less than your BMR, a higher amount of fat will be burnt.

Total calorie requirement = BMR + Activity Induced Requirement (walking, physically working etc. Each activity burns a specific amount of calories per hour)

Therefore if total calorie intake from food is less that total calorie requirement, you lose fat. If the intake exceeds the requirement, you put on.

Calculating your BMR:

There are two formulas you can use to calculate your BMR. The Harris-Benedict formula is the one you will use if you don’t know your Lean Body Mass. If you know your LBM, through an accurate test like DEXA whole body scan, you can use the Katch McArdle formula for getting the most accurate calorie estimate.

Harris-Benedict formula

Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)
Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) - (4.7 X age in years)
Note: 1 inch = 2.54 centimeters
1 kilogram = 2.2 lbs.

Katch-McArdle formula

BMR (men and women) = 370 + (21.6 X lean mass in kg)

Some people are genetically gifted, like cars that burn lot of fuel even while idling. When they become active, they zoom fast and burn off fuel at an enormous rate. For the normal people, knowing the BMR, and keeping control of the calories eaten and spent, is the only way to avoid or losing body fat.

The type, pace, duration and the timing of exercise plays a crucial role in proper fat loss, and I shall be writing about them in my subsequent posts…