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Energy requirements

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

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.


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