Energy expenditure calculation

Energy expenditure calculated from Schofield equation ... 

The present chapter deals with calculations associated with calories, nitrogen, protein-calorie percentage, parenteral hyperalimentation, and resting energy expenditure (REE) calculations including REE assessments for geriatric and pediatric populations. 

TABLE 11.2. Formulae for Resting Energy Expenditure (REE) Calculations. 

Sophisticated methods for assessing energy expenditures of hospitalized patients are now commercially available. One such method to calculate the REE involves the use of Vco, and V0, in expired air. An indirect calorimetric assay is employed to measure Vco, and V0, from the mechanically ventilated patient. REE can be calculated as follows ... 

Table 2.4 Empirical formulae for the calculation of resting energy expenditure of men and women with worked examples Harris Benedict (1919) for adults...

Average values for the REE are 7.02 MJ (1680 kcal) per day for normal weight standard adult males (i.e. 70 kg) and 5.60 MJ (1340 kcal) per day for normal weight standard females (i.e. 58 kg). These values conceal as much as 30% variation between individuals, which is greater than changes in energy expenditure caused by normal levels of physical activity or by changes in ambient temperature. (Note difference for a female when calculated from schoheld equations presented above.)... 

Quantitative studies of energy metabolism and fuel utilisation in very prolonged physical activity were performed by Mike Stroud during his Antarctic expedition with Ranulph Fiennes in 1992. One part of the study was measurement of energy expenditure by the dual isotope techniques (Chapter 2). Calculated over the whole expedition, the average daily energy expenditure of Stroud and Fiennes was 29 MJ but on particularly arduous days it increased to... 

The method used for measuring energy expenditure of patients is indirect calorimetry, aldiough it can be calculated from die Harris Benedict or Schofield equations (Ch ter 2). 

Survival time is calculated on the assumption of a basal energy expenditure of 1,800 kcal/day. 

Consider an amphipod with a body weight of 10 xg consuming 4.0 X 10-9 mol oxygen every hour at steady state and eliminating 3.6 X 10 9 mol carbon dioxide, 0.4 X 10-9 mol N (as ammonia), and 0.1 X 10-9 mol lactic acid. The external work power is 50 X 10-9 W. The heat loss of the animal may be calculated when the following four net reactions contribute to the energy expenditure ... 

The energy expenditure may be calculated from the energy balance. Assume that (i) carbohydrate (CH), fat (F), and protein (Pr) are the only compounds involved in the oxidation process (ii) the other compounds are stationary and (iii) the uptake and elimination of oxygen, carbon dioxide, and nitrogen is instantaneous. From the first law of thermodynamics, we have... 

A small organism has a heat loss of -< = 1.65 W and performs external work W = 0.025 Nm/s. Calculate that part of the total energy expenditure that originates from its internal circulation, which involves the pumping of 122mL/min of fluid against a pressure drop of 3.4 kPa with a net chemo-mechanical efficiency of 12%. 

In view of the central role of the nicotinamide nucleotides in energy-yielding metabolism, and the fact that, at least in theory, the nicotinamide released by ADP-ribosyltransferase (Section 8.4.2) and poly(ADP-ribose) polymerase (Section 8.4.3) is available to be reutilized for nucleotide synthesis (although this may not occur when these enzymes are significantly activated), niacin requirements are conventionally calculated on the basis of energy expenditure. 

The depletion/repletion studies of Horwitt et al. (1956) and others have suggested, on the basis of restoration of urinary excretion of -methyl nicotinamide, that the average niacin requirement is 5.5 mg per 1,000 kcal (1.3 mg per MJ). Allowing for individual variation, reference intakes (see Table 8.2) are set at 6.6 mg niacin equivalents (preformed niacin - -1 /60 of the dietary tryptophan) per 1,000 kcal (1.6 mgper MJ). Even when energy intakes are very low, it must be assumed that energy expenditure will not fall below 2,000 kcal, and this is the basis for the calculation of reference intakes for subjects with low energy intakes. 

Calculating Energy Expenditures Direct Calorimetry Metabolic Rate... 

The use of direct calorimetry is not a convenient technique, since it requires a specially constructed room and the confinement of human subjects for a day or longer in the room. The doubly labeled water technique offers a convenient alternative, providing that one has a machine to perform isotope ratio mass spectrometry. The doubly labeled water technique is used to measure the rate of total CO2 production in the body. This number alone is not sufficient to allow one to calculate the total energy expenditure. But the value for COj production (moles COi/day), along with the RQ, allows one to calculate the oxygen consumption using the following formula ... 

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