energy requirements

Last reviewed 08/2018

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.