To calculate the total caloric requirement, first the patient’s basal energy expenditure (BEE, also called basal metabolic rate, BMR) needs to be calculated.
BEE/BMR is the energy needed to carry out fundamental metabolic functions such as breathing, ion transport, normal turnover of enzymes etc. Harris Benedict equations are often used to calculate BEE.
BEE {men} = 66.5 + 13.75W + 5H - 6.78A
BEE {women} = 655.1 + 9.56W + 1.85H - 4.68A
Here,
W = Weight in kg,
H = Height in cm, and
A= Age in years
After the BEE is calculated one needs to take physical activity and stress levels into account to calculate the total daily expenditure (TDE). The TDE is calculated by multiplying BEE by the activity level and by any additional stress factors.
TDE = BEE × Activity Factor × Stress Factor
Activity factors
- Confined to bed 1.2
- Ambulatory 1.3
Stress factors (use 1 for non-stressed patients)
- Surgery 1.2
- Infection 1.4
- Trauma 1.5
- Burns 1.7
Example
Calculate the BEE and TDE for a 65 year old female measuring 5 feet 2 inches and weighing 150 lb. The patient has an activity factor of 1.2 (confined to bed) and a stress factor of 1.2 (surgery).
Convert weight and height to kg and cm, use the BEE (women) equation and the TDE equation with appropriate activity and stress factors.
- Patient’s weight = 150 lb = (150 ÷ 2.2) kg = 68.18 kg
- Patient's height = 62 inches = (62 × 2.54) cm = 157.48 cm
BEE {women} = 655.1 + 9.56W + 1.85H - 4.68A = 655.1 + (9.56×68.18) + (1.85×157.48) – (4.68×65) = 1294.04 kcal
TDE = 1294.04 × 1.2 × 1.2 = 1863.42 kcal
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