The Calories Needed to Maintain Weight

Overview

You must consume fewer calories than you burn in order to lose weight. After you achieve your weight goal, you’ll need to eat the same number of calories that you burn to maintain your weight. You can estimate your calorie requirements with equations that use a variety of physical factors.

Factors

The most important factors that affect your calorie expenditure are your lean body mass and your activity level. Lean body mass is your body weight that isn’t due to fat and is important because muscle requires more energy than fat. A person with a high lean body mass will burn more calories than someone with a higher lean body mass even though they have the same weight. Your activity level also directly affects your calorie expenditure rate.

Lean Body Mass

You can estimate your lean body mass from physical measurements. The formula for women is (weight x 0.732) + (wrist / 3.14) + (forearm x 0.434) — (hips x 0.249) — (waist x 0.157) + 8.987. The formula for men is (weight x 1.082) — (waist x 4.15) + 94.42. The weight in these formulas is in pounds and all other measurements are in inches.

Basal Metabolic Rate

Your basal metabolic rate, or BMR, is your calorie expenditure rate when you aren’t performing any activity at all. The most accurate method of obtaining your BMR is by directly measuring it under laboratory conditions. You can also estimate your BMR with standard equations.

Katch-McArdle Equation

The Katch-McArdle Equation provides your BMR from your lean body mass. This equation is (9.82 x lean body mass) + 370 where your lean body mass is in pounds. The Katch-McArdle Equation calculates your BMR in calories per day.

Assume your lean body mass is 141 lbs. Your BMR is (9.82 x lean body mass) + 370 = (9.82 x 141) + 370 = (1,385) + 370 = 1,755 calories per day.

Activity Factor

Your actual calorie requirement is the product of your BMR and your activity factor. Your activity factor is 1.2 if you’re sedentary, 1.375 if you exercise lightly two to three times per week and 1.55 if you’re moderately active. You activity factor is 1.725 if you exercise heavily 6 to 7 times per week and 1.9 if your job is physically demanding.

Assume your BMR is 1,755 calories per day and you engage in light exercise three times per week. Your activity factor is 1.375, so your calorie requirement is 1,755 x 1.375 = 2,413 calories per day.

About this Author

Allan Robinson has written numerous articles for various health and fitness sites. Robinson also has 15 years of experience as a software engineer and has extensive accreditation in software engineering. He holds a bachelor’s degree with majors in biology and mathematics.