Fundamentals of Food Technology

Indirect Calorimetry

• Indirect Calorimetry is based on the principle that when an organic substance is completely combusted either in calorimeter or in the human body, oxygen is consumed in amounts directly related to the energy liberated as heat.
• In this method oxygen consumed and carbon dioxide excreted in a given time under basal condition is measured.
• Many experiments on people of different ages have shown that 1 litre of oxygen is equal to 4.825 kcals when the person is in Basal Metabolic condition.

• The basal metabolic rate is measured by indirect calorimetry.

• The person has to observe certain conditions before measuring the basal metabolic rate.
  

They are:

1. In a post-absorptive state i.e., 12-16 hours after the last meal preferably in the morning.

1. In a reclining state but awake.
2. Before the test the person must take one hour rest if he is engaged in any work.
3. Relaxed and free from emotional upset, excitement or fear.
4. Body temperature must be normal
5. Room temperature must be comfortable.

• In these favourable conditions the BMR is measured.

• For an adult man the BMR rate is 34.2-36.7 kcals/sqm/hr.

• For an adult woman 30.9-35.1 / kcals/sqm/hr.

• For 7-8 years boys it is 49.1 / kcals / sqm/hr.

• For girls it is 45.2 / kcals/sqm/hr.

• For children it is more.