Caloric Needs

An individual’s caloric needs can be calculated by determining their basal metabolic rate (BMR) and multiplying by an activity factor to account for energy used by intensity and frequency of exercise. If you do not know body fat/lean mass, the best way to estimate caloric needs is the Harris-Benedict equation. This equation will be very accurate in all but the very muscular (will under-estimate calorie needs) and the very overweight (will over-estimate calorie needs) because it does not take into consideration lean body mass as a variable. In addition, different equations are used for men and women.

Caloric Needs = BMR x Activity Factor

Calculating the "Activity Factor"

Activity Level Activity Factor
Little to no exercise 1.2
Light exercise (1-3 days per week) 1.375
Moderate exercise (3-5 days per week) 1.55
Heavy exercise (6-7 days per week) 1.725
Very heavy exercise (twice per day, extra heavy workouts) 1.9

Calculating BMR

An online calculator can also help to determine BMR and a simple calculation using the activity factor will provide caloric needs.

BMR = (10 x weight in kg) + (6.25 × height in cm) - (5 × age in years) – 161

For example, a 37 year old, sedentary, 5 foot, 9 inch (175.3 cm), woman weighing 164 pounds (74.4 kg) would have a calculated BMR of 1493.6. The calculation is [(10 x 74.4) + (6.25 x 175.3) – (5 x 37) – 161] = [744 + 1095.6 – 185 -161]. Because she is sedentary, her Harris-Benedict equation suggests an activity factor of 1.2 making her caloric needs 1792.32 per day or roughly 1800 calories.

(10 x weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

For example, a 37 year old, sedentary, 5 foot, 9 inch (175.3 cm), man weighing 164 pounds (74.4 kg) would have a calculated BMR of 1659.6. The calculation is [(10 x 74.4) + (6.25 x 175.3) – (5 x 37) + 5] = [744 + 1095.6 – 185 + 5]. Because he is sedentary, his Harris-Benedict equation suggests an activity factor of 1.2 making his caloric needs 1992 per day or roughly 2000 calories.

Individuals who are younger, more active, taller, and heavier have greater caloric needs. If you do have body fat/lean mass then you can use the Katch-Mcardle formula. The Katch-Mcardle formula requires determination of lean body mass which is Weight in kg x (100-(Body Fat)) / 100. Then, BMR is calculated as (21.6 x Lean Body Mass in kg) + 370. BMR is multiplied by the activity factor to determine one’s daily caloric needs.