Total Caloric Requirements
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 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.
$$ BEE_{men} = 66.5 + 13.75 \ W + 5 \ H - 6.78 \ A $$
$$ BEE_{women} = 655.1 + 9.56 \ W + 1.85 \ H - 4.68 \ A$$
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.
$$ TDE = BEE \times Activity \ Factor \times Stress \ Factor $$
| Activity factors | Stress factors ( use 1 for nonstressed patients) |
|---|---|
| Confined to bed 1.2 | Surgery 1.2 |
| Ambulatory 1.3 | Infection 1.4 |
| Trauma 1.5 | |
| Burns 1.7 |
|
Solved Problem: 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).: Approach: : Convert weight and height to kg and cm, use the BEEwomen equation and the TDE equation with appropriate activity and stress factors. $$ Patient's \ weight = {150 \ lb} \times {1 \ kg \over 2.2 \ lb} = 68.18 \ kg $$ $$ Patient's \ height = 62 \ inches \times {2.54 \ cm \over 1 \ inch } = 157.48 \ cm$$ $$ BEE_{women} = 655.1 + 9.56 \ (68.18) + 1.85 \ (157.48) - 4.68 \ (65) = 1294.04 \ kcal$$ $$ TDE = 1294.04 \ kcal \times 1.2 \times 1.2 = 1863.42 \ kcal$$ Answer: 1294 kcal, 1863 kcal |