The number of calories needed by an adult per day depends on the gender, body size, muscle mass, health status and hormones, as well as individual variation in metabolism, according to L.K. Mahan and Sylvia Escott-Stump in "Krause's Food, Nutrition and Diet Therapy." The body at rest needs energy for basic functions, such as metabolism, breathing and circulating blood. Physical activity requires an additional amount of energy.
Collect Measurements
Step 1
Measure height, without shoes, in feet and inches using a tape measure. Measure weight in pounds using a bathroom scale. Ascertain age in years. Record height, weight and age on the paper.
Step 2
Convert weight in pounds to kilograms. Divide the weight in pounds by 2.2 to get the weight in kilograms. For instance, a woman who weighs 155 lbs. would weigh 155 / 2.2 = 70.5 kilograms. Record the weight in kilograms.
Step 3
Convert height in feet and inches to centimeters. A woman whose height is 5 feet 7 inches would be 5 x 12 plus 7 inches or a total of 67 inches tall. There are 2.54 centimeters per inch, so her height in centimeters is 67 x 2.54 or 170 centimeters. Record the height in centimeters.
Calculate
Step 1
Calculate the Resting Energy Expenditure, or REE. The Harris-Benedict equation for women, according to "Krause's Food, Nutrition and Diet Therapy," is: REE calories = 655 + 9.56 W + 1.85 H -- 4.68 A. The Harris-Benedict equation for men is REE calories = 66.5 + 13.75 W + 5.0 H -- 6.78 A, where W = weight in kilograms, H = height in centimeters and A = age in years.
Plug the values for weight, height and age into the Harris-Benedict formula in place of the W, H and A. For example, for a 45-year-old woman who is 5 feet 7 inches tall and weighs 155 lbs., the equation for women becomes 655 + (9.56 x 70.5 kg) + (1.85 x 170 cm) - (4.68 x 45 years old) = 1,433 calories REE. Record the calculated REE.
Step 2
Select the appropriate physical activity factor. The physical activity factor, according to "Krause's Food, Nutrition, & Diet Therapy," is a constant that will be multiplied by the REE to account for the energy needed for work, daily activities and play. For example, here are few physical activity factors: 1.2, if chair bound or bed bound; 1.45, if seated work with no moving around and little if any strenuous activity; 1.65, if seated work with moving around but little or no strenuous activity; 1.85, if standing work, such as housework, shop assistant; +0.3, if significant amount of strenuous activity, 30 to 60 minutes per day, four to five times per week; and 2.2, strenuous work or highly active leisure.
Suppose the woman in the example normally expends energy in seated work with some moving around, but little or no strenuous activity. Her physical activity factor is 1.65. Record the selected physical activity factor.
Step 3
Multiply the REE by the appropriate physical activity factor. Continuing the example, 1,433 calories x 1.65 = 2,364 total calories needed per day.
Tips and Warnings
- A quick ballpark estimate or rule of thumb for adults is based on calories per kilogram. For men whose level of activity is light, estimated calories per day equals kilograms times 38. For women whose level of activity is light, estimated calories per day equals kilograms times 35, according to Eleanor Whitney and Sharon Rolfes in "Understanding Nutrition." In the previous example, estimated calories per day is approximately 70.5 x 35 = 2,468 calories per day. The USDA/ARS Children's Research Center at Baylor College of Medicine provides an online calculator for adult calorie needs.
Things You'll Need
- Tape measure
- Scales
- Calculator
- Pencil
- Paper
References
- "Krause's Food, Nutrition, & Diet Therapy, 10th Edition"; L.K. Mahan and S. Escott-Stump; 2000
- "Understanding Nutrition, Ninth Edition"; Eleanor Noss Whitney and Sharon Rady Rolfes; 2002
- USDA/ARS Children's Research Center at Baylor College of Medicine: Adult Energy Needs
- Highlands.edu: Energy Balance and Weight Control
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