The calories an individual consumes everyday is contingent upon different factors. In fact, those factors are what differentiates you from the person sitting next to you; your caloric intake will not be the same. The understanding of the energy balance equation and the total daily energy expenditure equation will substantiate this immutable premise.
The Energy Balance Equation
The energy balance equation consists of 2 prime factors; energy intake and energy output. Energy intake is what you are putting into your body such as food and drinks. On the other hand, energy output consists of your basal metabolic rate, thermic effect of food and physical activity done during the day.
Adjusting the energy equation to meet your goals:
Weight Maintenance: Energy intake = energy output
Weight Gain: Energy intake > energy output
Weight Loss: Energy intake < energy output
What is TDEE and how to use it to manage your diet?
TDEE stands for total daily energy expenditure. It is the energy output (energy you exert) part of the energy balance equation. TDEE is defined as the net calories that the body burns in a given day. It consists of 3 interacting factors:
Basal metabolic rate (BMR): It is what the body burns when your body is at rest and not digesting food. This consists of 65-70% of your daily energy expenditure.
Thermic effect of food (TEF): It is the amount of energy that is needed to ingest, digest and store food. This consists of 6-10% for men and 6-7% for women.
Thermic effect of activity (TEA) : It is the energy burnt during physical activity whether it is a planned workout or unplanned such as walking in the mall. TEA accounts for 20-40% of total daily expenditure.
The Harris-Benedict equation
The Harris-Benedict equation is a well known tool that is used to calculate total daily energy expenditure. It uses factors such as an individual's gender, height, weight, age and amount of physical activity. The equation is split into two parts; the BMR and Activity multiplier.
How to calculate BMR for:
MEN: 66 + ( 13.7 x weight in kg ) + ( 5 x height in cm ) - ( 6.8 x age )
WOMEN: 655 + ( 9.6 x weight in kg ) + (1.8 x height in cm ) - ( 4.7x age )
How to calculate Activity multiplier:
After finding out your BMR, you can calculate your TDEE by multiplying your BMR with your activity multiplier. The following table shows your activity multiplier factor based on the amount of physical activity that you do.
Example:
I am a female.
I am 22 years old.
My height is 168cm.
My weight is 56.5 kg.
My BMR would be: 665 + (542) + (302) - (103) = 1395 calories/day
My activity level is moderately active (workout 3-5 days/week)
My activity factor is 1.55
My TDEE = 1.55 x 1395= 2162 calories/day.
If you would like to lose weight, it is advised to subtract 250 calories from your daily calories.
Limitations of the Harris-Benedict equation
Due to the fact that the equation does not account for the variable of lean body mass, the equation will not be very accurate for those who are extremely muscular and the extremely overweight. It tends to underestimate the caloric needs of those that extremely muscular and overestimate the caloric needs for those that are extremely overweight. Other than those outliers, the equation is very accurate for the majority of people.
References
Active IQ. (2014). Active IQ manual L2 gym instructor. Cambridgeshire, UK: Active IQ LTD.
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