Human Nutrition 3(3+0)

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

General principles

The general principles of measuring energy metabolism are

• Measuring the volume of expired air during work for fixed periods of 5 to 10 minutes.
• Collection of a sample of expired air for the analysis of O2 and CO2contents.
• Calculation of O2 consumption, CO2 output and R.Q.; and
• Calculation of the energy output from the R.Q. and O2 consumption.

Factorial method for calculating the daily energy requirement:

1. The daily calorie requirements of an adult man (65 kgs) for varying degrees physical activity.(sedentary, light work, moderate and heavy work)
2. To this, 8% extra calories are added to meet the needs of S.D.A. of food.
3. Total calories are expressed as percentage of basal metabolism.
4. The extra energy required for work over basal metabolism is termed as activity increment.

Table: Energy expenditure * per day (kcal) for various types of activities (Adult 65kgs. – 25 years)

	Sedentary work	Light work	Moderate work
Sleep eight hours	480	480	480
Work six hours	720	1350	2250
Recreation four hours	480	480	480
Walking one hour	225	225	225
Houshold wok and gardening four hours	480	480	480
	2385	3015	3915
SDA of food (8%)	190	240	312
Total calorie requirements(k.cal)	2575	3255	4227

*Basal metabolism =1,625 k.cal.