The Mifflin Equation and "Activity Factor"
If you want a specific answer to "how many calories do I burn in a normal day," apply the Mifflin equation to calculate the Basal Metabolic Rate (BMR).
The Mifflin equation for men is: (10 x weight in kgs) + (6.25 x height in cms) - (5 x age in years) + 5.
The Mifflin equation for women is : (10 x weight in kgs) + (6.25 x height in cms) - (5 x age in years) – 161.
These equations requre their weight in Kgs and height in centimeters. One inch equals 2.54 cerntimeters, and one lb equals 0.45359237 kg.
Next, multiply the BMR obtained from the Mifflin equation by an "Activity Factor" derived from the Harris Benedict equation, to obtain the calories burned.
The "Activity Factor" is an index based on one's lifestyle, and is listed in the Harris Benedict equation. An "Activity Factor" of 1.2 denotes a "Sedentary Lifestyle" with a desk job and little or no exercise. An "Activity Factor" of 1.375 denotes a "Lightly Active Lifestyle" with light exercises, an "Activity Factor" of 1.55 denotes a "Moderately Active Lifestyle," an "Activity Factor" of 1.725 denotes a "Very Active Lifestyle" accompanied by hard exercise or sports, and an "Activity Factor" of 1.9 denotes an "Extremely Active Lifestyle" centered on exercise, sports or a physical job.
To illustrate, consider the case of a thirty year old female 167.6 cm tall and 54.5 kg heavy, with a desk job.
- BMR = (10 x 54.5) + (6.25 x 167.6) + (5 x 3) – 161 = 1446.5 calories (k.cals)
- Activity factor = 1.2
- Calories Burned in a normal day = 1446.5 x 1.2 = 1735.8 calories (k.cal) per day