Energy needs

Energy requirement is considered to be equal to measured or assessed energy expenditure. By feeding a patient, we try to replace oxidized endogenous substrates by diet-derived substrates. Therefore it should be more appropriate to consider nutrient balance rather than energy balance.

The energy production rate of a patient in basal conditions (supine subject in a thermoneutral environment and after a 12-h fast) can be determined by indirect calorimetry, calculated using formulas, or estimated.

Measurement may be appropriate in more clinically unstable and catabolic patients, particularly those with respiratory failure, and in patients requiring prolonged intensive treatment. Basal energy production rate (kcal/day) is predicted by the Harris-Benedict equations:

males: 66.473+(13.752 x weight) + (5.003 x height) - (6.755 x age)

females: 655.095 + (9.563 x weight) + (1.850 x height) - (4.676 x age)

where weight is in kilograms, height is in centimeters, and age is in years. These equations should only be corrected for stress (final value no more than 1.15 to 1.25 times the calculated value except for burned patients). Calculated or measured values, minus the amount of energy derived from protein oxidation (nitrogen loss (g) x 26.6), are utilized to plan the non-protein calorie intake. In overweight patients we suggest using the formula with the ideal body weight to avoid further overstimation.

A rough estimate of 20 to 35 kcal/kg is reasonably adequate in clinical practice.

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Keep Your Weight In Check During The Holidays

A time for giving and receiving, getting closer with the ones we love and marking the end of another year and all the eating also. We eat because the food is yummy and plentiful but we don't usually count calories at this time of year. This book will help you do just this.

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