The BMR (Basal metabolic rate) can be calculated by measuring oxygen consumption and CO 2 production, but it is more usually taken from standardized tables ( Table a ) that require knowledge of the subject's age, weight and sex.
| Table (a) - Equation for the prediction of Basal metabolic rate (in MJ per day) |
| Age Range (years) |
Prediction equation (BMR=) |
95% Confidence limits |
| Men |
| 10-17 |
0.074 (wt)* + 2.754 |
+/- 0.88 |
| 18-29 |
0.063 (wt)* + 2.896 |
+/- 1.28 |
| 30-59 |
0.048 (wt)* + 3.653 |
+/- 1.40 |
| 60-74 |
0.0499 (wt)* + 2.930 |
N/A |
| 75+ |
0.0350 (wt)* + 3.434 |
N/A |
| Women |
| 10-17 |
0.056 (wt)* + 2.896 |
+/- 0.94 |
| 18-29 |
0.062 (wt)* + 2.036 |
+/- 1.00 |
| 30-59 |
0.034 (wt)* + 3.538 |
+/- 0.94 |
| 60-74 |
0.0386 (wt)* + 2.875 |
N/A |
| 75+ |
0.0410 (wt)* + 2.610 |
N/A |
| |
| *Bodyweight (wt) in kilograms |
| Table (b) - Physical activity ratio (PAR) for various activities (expressed as multiples of BMR) |
| |
PAR |
| Occupational activity |
| Personal/Housewife |
1.7 |
| Domestic helper/Sales person |
2.7 |
| Labourer |
3.0 |
| |
|
| Non-Occupational activity |
| Reading/Eating |
1.2 |
| Household/Cooking |
2.1 |
| Gardening/Golf |
3.7 |
| Jogging/Swimming/Football |
6.9 |
Physical activity. The physical activity ratio (PAR) is expressed as multiples of the BMR for both occupational and non-occupational activities of varying intensities ( Table b )
 Thus, for example, to determine the daily energy expenditure of a 55-year-old, 50 kg female doctor, with a BMR of 5240 kJ per day spending one-third of a day sleeping, working or engaged in non-occupational activities, the latter at a PAR of 2.1, the following calculation ensues:  In the UK the estimated 'average' daily requirement is:
- for a 55-year-old female - 8100 kJ (1940 kcal)
- for a 55-year-old male - 10 600 kJ (2550 kcal).
This is made up of 50% carbohydrate, 35% fat, 15% protein plus or minus 5% alcohol. In developing countries, however, carbohydrate may be more than 75% of the total energy input, and fat less than 15% of the total energy input.
Energy requirements increase during the growing period, with pregnancy and lactation, and sometimes following infection or trauma. In general, the increased BMR associated with inflammatory or traumatic conditions is counteracted or more than counteracted by a decrease in physical activity, so that total energy requirements are not increased.
In the basal state, energy demands for resting muscle are 20% of the total energy required, abdominal viscera 35-40%, brain 20% and heart 10%. There can be more than a 50-fold increase in muscle energy demands during exercise.
Energy Expenditure
Energy Stores
Basal Metabolic Rate
Recommended healthy diet
Dietary requirements
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