Maintaining a healthy weight throughout your life is not only good for your health, it's also good for the quality of life, too, says the 2010 Dietary Guidelines for Americans. Calorie balance is key to weight control. While there are a number of mathematical equations used to determine calorie needs, some include height, weight and age. Consult your doctor or dietitian to help you determine your calorie needs.
Height, Weight and Age for Calories
Equations that use your height, weight and age to determine your calorie needs generally estimate your basal metabolic rate. Your BMR is the number of calories your body needs for basic bodily functions, including the maintenance of organs and tissue, heartbeat and respiration.
The Harris-Benedict equation is commonly used because it is considered quick and easy, according to Kent State University. The equation is different for men and women.
For men, the formula is: 66 + (6.23 X weight in pounds) + (12.7 X height in inches) - (6.8 X age in years).
For women, it is: 655 + (4.35 X weight in pounds) + (4.7 X height in inches) - (4.7 X age in years).
So, for example, a 6-foot tall 45-year-old man weighing 208 pounds has a BMR of 1,970 calories (66 + 1295.84 + 914.4 - 306).
The BMR equation provides a baseline for your calorie needs, but it's not the whole picture. Your total daily calorie needs also include activity factors. Factors range from 1.2 for people with a desk job and very little activity to 1.9 for people training for a triathlon. Your BMR is multiplied by these factors to determine your daily calorie needs. For example, if the 45-year-old man exercises three days a week, you can determine his daily calorie needs by multiplying his BMR by an activity factor of 1.375, which means he needs 2,709 calories to maintain his current weight.
Other Ways to Estimate Calories
While the Harris-Benedict formula is most often used to estimate calories based on weight, height and age, it's not the only formula. The University of Colorado at Denver reports that the Mifflin equation is a more accurate formula for estimating BMR. Like Harris-Benedict, this formula is also gender-specific.
The Mifflin formula for estimating BMR for men is: (10 X weight in kilograms) + (6.25 X height in centimeters) - (5 X age in years) + 5.
For women, it is: (10 X weight in kilograms) + (6.25 X height in centimeters) - (5 X age in years) - 161. Divide weight in pounds by 2.2 to get kilograms, and multiply height in inches by 2.54 to get centimeters.
The Mifflin formula estimates the 6-foot-tall, or 182.9 centimeters, 208-pound, or 94.5 kilograms, 45-year-old man's BMR as 1,868 calories (945+1143.125-225+5).
Benefits of Knowing Your Calories
No matter where your weight is on the scale, knowing your calorie needs based on your weight, height and age can help you swing the number in your desired direction. If you're trying to lose weight, you need to eat fewer calories than the number of calories predicted, and if you're trying to gain, you need to eat more. If you're already at your desired weight, closely monitoring your intake can help you stay in balance. Getting to and maintaining a healthy weight is key to overall good health.