Human Nutrition 3(3+0)

Lesson 9 : BMR-Methods of Measurements and Factors Affecting BMR

Determination of Basal Metabolism

Basal Metabolism is usually determined using the apparatus of Benedict and Roth. The apparatus is a closed circuit system in which the subject breathes, in oxygen from a metal cylinder of about 6-litre capacity and CO2 produced is absorbed by soda- lime present in the tower. The oxygen cylinder floats on water present in an outer tank. The subject wears a nose clip and breathes the oxygen present in the cylinder for a period of 6 minutes through a mouthpiece. The volume of O2 used is recorded with a pen on a graph paper attached to a revolving drum. Since the subject is in the post –absorptive state, R.Q. is assumed to be 0.82 and the calorific value of one liter of O2 consumed is taken as 4.8 Kcal.

Example:

Subject:

Adult, male, Body weight- 50 kg
Oxygen consumed in 6 minutes = 1,100ml
Heat produced in 6 minutes = 4.8*1.1 =5.28 Kcal
Heat produced in 24 hours =5.2*10*24 =1,267Kcal.

The basal metabolism of the individual for 24 hours = 1,267 Kcal.