BMI & BMR
Your BMI is an indirect measure of your body composition — or how much body fat you have. Although BMI doesn’t measure body fat directly, it uses your weight and height to determine whether you’re classified as underweight, normal weight, overweight or obese. This measurement correlates moderately well with other measurements of body fat such as skinfold measurements and underwater weighing.
BMI is measured by dividing your weight in pounds by the square of your height in inches, then multiplying by 703. The equation looks like this: BMI = (weight / height x height) x 703.
If you’re a woman who is 125 pounds and 5 feet 4 inches, your BMI = (125 / 64 x 64) x 703 = 21.4. This BMI puts you in the normal weight range.
A BMI below 18.5 indicates that you’re underweight; a BMI between 18.5 and 24.9 classifies you as a normal weight; a BMI between 25 and 29.9 puts you in the overweight category; a BMI of 30 or above classifies you as obese.
The amount of energy (in the form of calories) that the body needs to function while resting for 24 hours is known as the basal metabolic rate, or BMR. This number of calories reflects how much energy your body requires to support vital body functions if, hypothetically, you were resting in bed for an entire day. In fact, your BMR is the single largest component (upwards of 60 percent) of your total energy burned each day.
The release of energy in this state is sufficient only for the functioning of the vital organs, such as the heart, lungs, brain and the rest of the nervous system, liver, kidneys, organs, muscles and skin. BMR decreases with age and with the loss of lean body mass. Increasing muscle mass increases BMR.
To really get how much time you should be exercising, you first have to look at your basal metabolic rate, or BMR. This is the amount of energy (calories) you burn at rest and which your body uses up just surviving. The basic rule of thumb is that you absolutely must net at or above your BMR in terms of caloric intake. This means that, when you subtract the amount of exercise calories you’ve burned from your total calories for the day, the difference is at least what your body needs to support fundamental physiological processes.
The above calculator is fully functional, so if you want to use it yourself, go ahead. Please note it can’t replace a professional medical advice! If you are planning an aggressive weight loss diet, better consult a doctor. The results of your calculations are for illustrative purposes and are approximate.