3 Methods to Calculate Total Daily Energy Expenditure and Why It’s Important for Weight Loss
Total Daily Energy Expenditure (TDEE) is a measure of the amount of energy you consume during the day. It’s made up of your Basal Metabolic Rate (BMR), which is the energy you use to stay alive, and the energy you use to do everything else (walk, talk, eat, and exercise).
BMR varies from person to person and between the sexes. Men tend to have a higher BMR than women of the same weight and height. This is because men have less fat than women. Other factors that can affect BMR include:
Height,
weight,
age, (BMR decreases by about 2% per decade after age 20)
how your thyroid behaves (Thyroxin is a BMR regulator),
diet (starvation diets lower your BMR)
internal temperature,
outside temperature,
· Physical exercise.
There are many ways to estimate the TDEE, but the most commonly used are:
Quick and dirty (based on body weight)
The Harris-Bededict formula
The Katch – McArdle formula (where your lean body mass has been estimated)
We will use the following example for the calculations:
she is a 40 year old woman
5 feet 4 inches = 1.63m tall
150 lbs = 68 kg of weight
% Body Fat = 32%
She wants to lose weight.
The quick and dirty method:
To lose weight = 12 – 13 calories per pound of body weight
Maintenance = 15 – 16
To gain weight = 18 – 19
In our example, our lady would need to eat between 1,800 and 1,950 calories a day to lose weight.
The Harris-Benedict (HB) formula (when you don’t know your lean body mass)
Since this method does not contain a variable for lean body mass, it will underestimate the caloric needs of the extremely muscular and overestimate the needs of the extremely obese. You must first calculate the BMR and then add your activity factor to determine TDEE
Men: BMR = 66 + (13.7 x weight in kg) + (5 X height in cm) – (6.8 x age in years)
Women: BMR = 655 + (9.6 x weight in kg) + (1.8 x height in cm) – (4.7 x age in years)
For our example BMR = 655 + (9.6 x 68) + (1.8 x 163) – (6.8 x 40) = 1343 calories/day
The activity multiplier is estimated as follows:
Sedentary = BMR X 1.2 (little or no exercise, desk job)
Lightly active = BMR X 1,375 (light exercise/sports 1-3 days/week)
modification. active = BMR X 1.55 (moderate exercise/sports 3-5 days/week)
Very active = BMR X 1,725 (intense exercise/sports 6-7 days/week)
Extremely active = BMR X 1.9 (intense daily exercise/sports and physical labor or 2X day training i.e. marathon, contest, etc.)
Our lady estimates that she is Mildly Active, so her TDEE can be estimated at 1,375 x 1,343 = 1,846 calories/day.
The Katch-McArdle (KM) formula (when lean body mass is known)
Men and women BMR = 370 + (21.6 x lean mass in kg)
Our lady had her body fat percentage measured at her local gym at 32%, so her lean body mass would be 68 x (100 – 32)/100 = 46.24 kg
So your BMR = 370 + (21.6 x 46.24) = 1369
Your TDEE using this formula would be 1,375 x 1,369 = 1,882 calories/day
You can see that the KM and HB formulas produce very similar results of 1846 and 1882 calories per day, but this is just TDEE and needs to be adjusted because our lady wants to lose body fat. So how much could you reasonably cut your calorie intake to lose fat? Well, that’s like asking how long a piece of string is and would easily fill another article (hmm, I might write that one someday!). However, as a general rule of thumb, you might consider cutting your calories by 15-20% and increasing your exercise. to include moderate workouts 3 – 4 times a week. She decides to reduce her calories by 15%, so her total calories using all three methods are:
Questions and Answers = 1800
HB=1569
km = 1600
I can’t say for sure if you lost weight on either of these diets, but I’d like to bet that your results would be better with the latter two methods than the first. If you are trying to lose body fat; Good luck.