Losing weight is, at its core, about numbers. The number of calories you take in versus the number of calories you burn is at the crux of most diets. You won't know where to begin in your weight loss plans, however, unless you know your body's basic daily caloric needs.
Basal Metabolic Rate
Basal metabolic rate, or BMR, is your body's daily caloric requirement to sustain life while you are completely at rest. BMR is also commonly referred to as your metabolism. According to the Mayo Clinic, your body requires calories to maintain all the basic functions such as breathing, cell repair, circulation and growth. The BMR equation relies on variables such as height, weight, age and sex to factor each unique body's need.
BMR Equation
Due to the difference in muscle composition, men and women will use different equations. According to the BMR Calculator website, those equations are:
Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
Men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years)
(Ref 2)
Activity Level
Your activity level also plays a pivotal role in weight loss. The more active you are, the more calories you will burn daily; it may also increase your lean body mass, naturally raising your metabolism. The Harris-Benedict equation takes your BMR into consideration and attaches a value to activity levels ranging from sedentary to extremely active. Using the Harris-Benedict equation may help you determine what your true calorie needs are per day based on how active or inactive you choose to be.
Harris-Benedict Equation
To find your total daily calorie need based on activity level, according to the Harris-Benedict Equation, multiply your BMR by your activity factor:
Sedentary (little or no exercise) = BMR x 1.2
Lightly active (light exercise/sports 1-3 days/week) = BMR x 1.375
Moderately active (moderate exercise/sports 3-5 days/week)= BMR x 1.55
Very active (hard exercise/sports 6-7 days a week) = BMR x 1.725
Extra active (very hard exercise/sports & physical job or 2x training) = BMR x 1.9
Function
A 40-year-old woman weighing 140 pounds who is 65 inches tall would have a BMR of approximately 1,491. If this same woman is sedentary she would multiply her BMR by 1.2 to determine her daily calorie need; that would equal 1,789 calories.
A 30-year-old man weighing 200 pounds who is 72 inches tall would have a BMR of approximately 2,022. If this man plays golf twice weekly he would multiply his BMR by 1.375 to determine his caloric need, which would be about 2,780.
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