Total Daily Energy Expenditure or simply the TDEE is the number of calories we burn in a day. We expend energy for every function in order to stay alive or activity our body performs.
Whether we are having a stroll in the corridor or just lying on our couch the energy is being utilized in both conditions however the amount differs. This energy expenditure can be under the influence of visceral functions being carried on all the time like breathing, heart pumping, brain/neuronal activities and other organs’ activities.
The physical movements we do throughout the day also contribute to the energy usage by our body, in other words, even the slightest act of raising an eyebrow requires energy.
The TDEE is the metric that calculates this total energy usage by our body in a period of 24 hours. But how this TDEE is calculated, means how come TDEE knows your energy expenditure and how it calculates it?
Well, this guide will throw light on what the TDEE calculation is, what factors are involved in it and which formula is used to calculate TDEE.
Components of TDEE
Generally, the TDEE comprises two major categories, i.e the NREE and REE. The non resting energy expenditure (NREE) contains the energy utilization by your body in a non-resting (physical movement) phase. The NREE includes the following
- Thermal effect of exercise (TEE)
- Thermal effect of food (TEF)
- Non-exercise activity thermogenesis (NEAT)
The TDEE is the energy needed by our body in order to perform daily physical movements or exercises. While the TEF is the energy required for digestion, absorption and all the process related to food including eating. Lastly, the NEAT is the requirement of energy to perform everyday tasks, like simply sanding still, lying on a couch or working on your laptop.
As for the Resting Energy Expenditure (REE), the only variable included is the Basal Metabolic Rate or BMR. The BMR accounts for 70% of the total TDEE calculation while the remaining 305 energy utilization in the body is by NREE.
In order to calculate the TDEE, comprising the NREE and REE of an individual, several different equations have been proposed. The TDEE calculators available online utilizes these formulas that give the estimation of the BMR of a person.
Following are the equations that are used to calculate the BMR and ultimately determining the TDEE by multiplying with an accepted factor.
In 1919, J. A. Harris and F. G. Benedict proposed the Harris-Benedict equation in their book, “A Biometric Study of Baal Metabolism in Man”.
It is possible to calculate your TDEE using the Harris-Benedict Calculation, which utilizes your BMR and an activity factor. The formula basically is used to obtain your BMR which ultimately is utilized to calculate total daily energy expenditure (calories).
In comparison to other equations, the Harris-Benedict Equation does not take into account lean body mass, which is the sole factor left out. However, lean bodies require fewer calories than comparatively leaner bodies.
As a result, this equation couldn’t be considered accurate in all cases, for instance, the muscular who have more calorie requirements will undermine them while the extremely obese will over-estimate their calorie needs requirements.
The Harris-Benedict equation used to calculate the BMR in males and females respectively s given below
BMR = 66.4730 + (13.7516 x weight in kg) + (5.0033 x height in cm) – (6.7550 x age in years)
BMR = 655.0955 + (9.5634 x weight in kg) + (1.8496 x height in cm) – (4.6756 x age in years)
Since 1919, the human bodies have metabolically evolved a lot and thus the Harris-Benedict equation doesn’t seem fit to scientists. Moreover, this formula can’t be applied to individuals having excess body fat and as a matter of fact, individuals of the same height and weight vary significantly in their calorie requirements.
Considering the above mentioned uncertainties, the Harris-Benedict formula was revised by Roza and Shizgal in 1984 considering the resting energy requirements and body cell mass.
In the revelation of the Harris-Benedict equation, it was found that REE is dependent directly upon the body’s size, the mass of the cells while doesn’t really depend on the gender and age of the individual.
Therefore, the revised Harris-Benedict equation’s variables represent the direct relationship between body mass and body weight. The formula for the revised Harris-Benedict equation is given as
BMR for Males = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)
BMR for Females = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)
Mifflin St Jeor
As per the modern lifestyles and variations among the human bodies the Harris-Benedict equation was again revised in 1990. The Mifflin and ST Joer presented this formula for BMR evaluation which is then named after by them as the Mifflin St Jeor equation.
The Mifflin St Jeor version of the Harris-Benedict equation is considered to be more accurate and reliable than the former two. It takes into account the same variables as the previous ones however the multiplying factors differ in it.
The Mifflin St Jeor equation is considered as the standard technique for measuring caloric needs. Moreover, the WHO and FAO utilize for every calculation comprising the calorie evaluation.
Women: (10 x weight in kg) + ( 6.25 x height in cm) – (5 x age in years) – 161
Men: (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5
Another formula that is also widely accepted by expert dietitians is the Katch McArdle equation for BMR calculation. Body fat percentage and lean body mass are the variables that are used in the Katch McArdle Formula.
This method of estimating body fat is usually more accurate than other approaches which rely just on weight. The equation is based on the Mifflin-St Jeor equation, which estimates FFM (fat free mass or lean mass).
The individuals that know their body fat % can be more precise with this measurement. The Katch McArdle calculations are done by following the formula given below
BMR = 370 + (21.6*lean body weight in kg)
Another equation that is also utilized to calculate the BMR is proposed by J. J. Cunningham and since named after by him. When estimating the basal metabolic rate, the Cunningham equation incorporates lean body mass.
Studies have discovered that this equation is more accurate in athletes and those with more skeletal muscle mass because skeletal muscles are more metabolically active.
However, several options exist for estimating your lean body mass. Lean body mass equals your body fat % minus your body fat. The Cunningham equation for BMR calculation states
BMR = 500 + (22 x LBM)
One benefit of using this calculation to determine your BMR is, if you build more muscle to increase lean body mass, you'll require more calories and the Cunningham equation will reflect that.
After calculating the BMR from any of the equations mentioned above it is multiplied by an activity factor and exercise factor to determine the NREE components of the TDEE.
The following physical activity levels (or PAL) are the constants that are multiplied with the BMR calculations in order to estimate the TDE of a person
- Sedentary (little to no exercise) = BMR x 1.2
- Lightly Active (Exercise 1-3 times a week) = BMR x 1.3
- Moderately Active (exercise 4-5 times a week) = BMR x 1.55
- Very Active (6-7 days a week intense exercises) = BMR x 1.725
- Extremely Active (very intense exercises or physical job) = BMR x 1.9
For each type of activity and exercise factor, there is a corresponding quantity of energy expended. As mentioned, to calculate your TDEE you have to multiply this factor with the BMR (the amount of energy your body requires to stay alive).
Normally, making these calculations to figure out how much energy you use in a day may be time-consuming and difficult. However, you will not be required to master any of the mathematical equations to calculate your TDEE. The TDEE calculator is intended to assist you online in this matter.