Body mass index (BMI) is a measure of fatness which can be found using height and weight measurements. Children with higher BMIs can consume more calories in a day without gaining weight, though heavier children should consider having fewer calories in order to lose weight and achieve a healthier body composition. Using information involving your child's BMI, you can compute how many calories your child should consume in a day, also known as the calorie quota, based on your child's activity level.
Step 1
Measure your child's height. The CDC recommends removing any shoes and hair items before doing so. Then have your child stand against the wall in a non-carpeted area. Using a flat object like a ruler or book, lower it to the child's head until the object becomes perpendicular (at a right angle) with the wall. Mark this with a pencil and measure the distance in inches from the floor to the marking with a tape measure.
Step 2
Square the height measurement. This means to multiply the measurement by itself. For instance, if your child is 3 feet 4 inches, or 40 inches, then the square of the height would be 1,600 (40 x 40). Note: You must convert any feet into inches by multiplying by 12 before squaring the height.
Step 3
Calculate the child's basal metabolic rate according to gender. If your child is a boy, BMR = 66 + (BMI x height squared x 6.23 / 703) + (12.7 x height) -- (6.8 x age in years). If your child is a girl, BMR = 655 + (BMI x height squared x 4.35 / 703) + (4.7 x height) -- (4.7 x age in years). In other words, if you have a 4-year-old boy who is 3 feet 4 inches with a BMI of 14, his BMR will equal 745.31 [66 + (14 x 1,600 x 6.23 / 703) + (12.7 x 40) -- (6.8 x 4)]. BMR reflects the amount of energy expended in calories while at rest for the functioning of vital organs and is used for predicting your child's calorie quota.
Step 4
Use the Harris-Benedict equations to predict your child's calorie quota based on activity level and BMR. These equations general say to multiply your child's BMR by a factor of 1.2 through 1.9, depending on your child's level of activity. For instance, a non-active child would have a calorie quota of BMR x 1.2, whereas an extremely active child would have a calorie quota of BMR x 1.9. To illustrate, if your 3-foot-4-inch 4-year-old boy with a BMI of 14 is moderately active--e.g., sports/exercise three to five times a week--his calorie quota would be 1,155 calories (BMR x activity factor = 745.31 x 1.55). This means, if he consumed 1,155 calories each day, theoretically he would maintain the same body composition for his height and age.
Tips and Warnings
- The " / " symbol, as in 6.23 / 703, means to divide.
Things You'll Need
- Tape measure
- Pencil
- Calculator
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