How To Estimate Your Energy Requirements

In this post we will cover how you can estimate your energy requirements.

The doubly labelled water (DLW) technique is deemed among the most precise approaches to determine total energy expenditure. Although, its premium price limits its extensive application. There are however, several formulas that can also be utilized to assess energy expenditure including Harris-Benedict equation and Mifflin-St. Jeor equation.

Prior to proceeding with discussion, you should note that all methods applied in determining energy expenditure provide estimates as to an individual’s energy requirements and that  energy expenditure is dependent on individual factors such as height, physical activity, weight, age and gender. Hence, when a dietitian estimates individual energy requirements, he or she considers all these factors.

Dietary reference intakes are termed the most precise guides for estimating total energy requirements among healthy persons. Predictive formulas such as Harris-Benedict equation are also essential in estimating the minimal amount of energy required at rest, and in turn used to calculate energy requirements.

To calculate energy requirements using Harris-Benedict equation:

For males:

BEE (kcals/day) =66.5+ (13.8×W) +(5.0×H)- (6.8×A)

For females:

BEE (kcals/day) =655.1+ (9.6×W)) + (1.8×H)- (4.7×A)

Whereby BEE is the Basal Energy Expenditure

A-Age

W-Weight in kilograms 

H-Height in centimetres 

After determining BEE using this formula, you determine activity level and then multiply with the total BEE to determine your energy requirements.

The accuracy of all equations, however, decreases when adjusted to obese groups. As such, other techniques are usually employed when estimating energy requirements for obese persons. The Resting Metabolic Rate (RMR)is usually determined using the indirect calorimetry method. However, if it is not feasible to obtain RMR, the dietitian applies the Mifflin-St.Jeor equation using patient’s actual body weight for the approximation of RMR.

When estimating the energy requirements for patients with spinal cord injury, the indirect calorimetry method is usually used by dietitian. Although, if this method is not available during the acute phases of injury (between 1-28 days) the dietitian uses the Harris Benedict  formula, using patient’s admission weight and multiplying by activity factor of 1.1 and injury factor of 1.2.

For critical care patients, the indirect calorimetry method is usually used to measure the Resting Energy Expenditure (REE). Though, the dietitian is normally required to consider factors such as the daily variations in metabolic stress levels, changes in medicines provided or changes in the ventilator support in type or degree. The dietitian professionals use other formulas such as the Penn State equation, Swinamer equation and Brandi equation when indirect calorimetry cannot be performed.

There are various approaches to estimate energy requirements. Different methods are targeted to different groups though the most commonly applied method is the Harris-Benedict equation. From the equations, the estimated energy requirements are determined , and factors such as  age,  height and activity level considered.