Energy requirements

The daily energy requirements of the individual are highly variable. They are dependent on numerous factors e.g.:

• age
• sex
• amount of physical activity
• stage of ovarian cycle if female
• environmental temperature

The energy input of the diet can be roughly calculated using the following algorithm; it is useful for quantifying the nutritional support needed for the hospitalized patient:

• calculate the resting metabolic rate using the Harris-Benedict equation
• estimate the stress factor dependent on the patient's disease state (see submenu)
• estimate the activity factor
• estimate the dietary factor from dietary induced thermogenesis
• multiply all of the above terms to give energy requirements in kcal/kg/day

Practically, patients with uncomplicated disease processes require around 30 kcal/kg/day. Those exceptionally stressed e.g. multiple trauma victims, extensive operation, major sepsis, may require up to 40 kcal/kg/day.