Total Daily Energy Expenditure is a measurement that indicates the total energy a person expends during the course of a day. Of course, it is not a constant value, since different activities are performed every day.
The calculation of the TDEE (Total Daily Energy Expenditure) is taken as a reference to work on when establishing training and nutrition programs that aim to modify weight or lean mass. It is used to adjust food intake to achieve the desired effect on the body.
To calculate it, two variables are normally used, which are the Basal Metabolic Rate, or total calories expended by the body to maintain its functions under specific conditions, and the level of physical activity.
The Basal Metabolic Rate is the most relevant, since it accounts for about 70%-75% of the calories expended by the body. The level of physical activity accounts for approximately 20%.
How each variable is calculated
Although the TDEE has a formula. The two variables that compose it must be previously calculated.
Basal Metabolic Rate (BMR). It is the minimum energy required for the body to function under stable temperature conditions and without digestive activity. Its most common formula (Mifflin-St Jeor) is
BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5 (Men)
BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161 (Women)
The Physical Activity Level. It is calculated by taking into consideration, on the one hand, the deliberate physical activity that a person performs and its degree of intensity, but also whether their daily routine involves considerable physical strain or whether, on the contrary, they lead an eminently sedentary life.
The five categorizations are fairly well defined, and on that basis an index is applied, usually expressed as 1.2 to 1.9.
The lowest level considers that the person performs minimal daily activity, does not practice sports and remains seated or immobile most of the day. This is assigned a factor of 1.2.
The level considered as light exercise involves low-intensity physical activity performed occasionally (1-3 times per week) and the performance of a daily routine that, without being sedentary, does not have a high mobility component. This level has an assigned factor of 1.37.
The third level, moderate exercise, assumes that the person already has a regular exercise program that he/she completes consistently (3-5 times per week), without high physical demands, and that his/her daily activity involves movement. The factor assigned to this level is 1.55.
The fourth level, that of intense exercise, can be applied to people who follow a daily physical activity routine (6-7 days), and whose level of hardness is high enough to demand significant effort from their body. The factor assigned in this case is 1.72.
The highest level is the one that includes people whose training is focused on achieving results, so their sessions, which can be up to two per day, require a very high level of intensity that always lead to exhaustion. In this case a factor of 1.9 is applied. Also included in this group are those who have a job that requires constant physical activity, even if they do not follow a daily training program.
Reliability of Total Energy Expenditure
As with so many other indices, Total Daily Energy Expenditure does not provide totally accurate information, but it does provide sufficiently accurate information to be used in nutrition strategies.
Since there is no single universal formula for the calculation of one of the variables, the TMB, but several that use different equations, the result of the TDEE can vary depending on whether one or another is used.
It should also be noted that, in some cases, in order to make the calculation more accurate, a third variable is taken into consideration, such as the thermogenic effect of the food. This concept includes the amount of calories necessary for the food to be processed and assimilated by the body, but since it is a very small percentage, it does not have a great impact on the result.