Let’s Calculate your Metabolism!

Well, actually what we are about to calculate is your “maintenance calories,” that is the number of calories you would need to consume to maintain weight. There will be 2 steps in this process: 1) calculating BMR, and 2) calculating activity expenditure. Below are 3 calculators to choose from, because well, everyone likes choices:

Step 1: Calculating BMR

-The Mifflin-St Joer Equation: This is a good equation for calculating BMR that does not use body composition (% body fat/lean body mass). Because assessing body fat accurately is pretty tough this can be a good one to use, however, it’s pretty cumbersome compared to the other two I will layout.

For Women: BMR = (10 x weight in kg) + (6.25 x height in cm) – (4.92 x age) – 161

For Men: BMR = (10 x weight in kg) + (6.25 x height in cm) – (4.92 x age) + 5

*For those more imperially inclined to get kilograms (kg) divide pounds (lbs) by 2.2, and to get centimeters (cm) multiply inches by 2.54.

-The Katch-McArdle Equation: This is a great equation if you have an accurate measure of someone’s body fat percentage. It’s also a pretty quick and easy equation. Just to help there is a figure below that shows pictures of actual people so that you can easily assess your current state, but be honest with yourself, I know it can be hard. Because this equation accounts for lean body mass there isn’t much worry of gender difference and only one equation is needed.

BMR = 370 + (21.6 x Lean Body Mass in kg)

-The Aragon Equation: Really there are two Aragon equations created by Alan Aragon, hence the name. One using body fat %, and another one not needing it, the latter I will show a bit later. Personally, I prefer the Aragon equations in my own practice as they are quick, easy, and pretty accurately in line with the other calculators. The below equation uses body fat %, which is really a proxy for lean body mass. Again, use the body composition graphic to assist you here if you’re at all in question of what your body fat is, well, you should probably just use it anyways.

BMR = 25.3 x Lean Body Mass (LBM) in kg OR 11.5 x Lean Body Mass (LBM) in lbs Figure 2. Men Body Fat % Chart (legionathletics) Figure 3. Women Body Fat % Chart (legionathletics)

Step 2: Combining Activity with BMR

Next, we calculate your TDEE, which is how many calories you burn in a day if you remember from above. We do this by taking the BMR that you just calculated and use an activity factor/multiplier that assesses your NEAT and EAT combined. While there are more nuanced ways to calculate these things separately, this version makes the most sense for the majority of people. Below is both a general chart using standard daily activity multipliers as well as the Aragon Total Energy Expenditure (TEE) equation I mentioned earlier that doesn’t use body composition:

-Basic Activity Multiplier Chart: Take your BMR calculated from one of the 3 BMR equations above and multiply it by what you believe to be your activity level below. This is your total caloric cost of living; the energy you expend “in the gym” and out of it. Remember, most people overestimate their daily activity so maybe be a little conservative here.

Sedentary: 1.2 (little to no structured exercise, desk job)

Light Activity: 1.375 (light exercise/physical activity 3-5 days/wk)

Moderate Activity: 1.55 (moderate exercise/physical activity 3-5 days/wk)

Very Active: 1.725 (vigorous exercise/physical activity 6-7 days/wk)

Extremely Active: 1.95 (vigorous exercise/physical 6-7 days/wk and a labor-based job) -Aragon TEE Equation: Don’t let the “TEE” portion confuse you, it’s essentially interchangeable with TDEE. I personally use this method with most clients as it is very simple and is pretty accurate compared most other equations. This equation uses one’s target body weight and multiplies it by a gender-equated training intensity combined with training hours per week. Similar to the activity factors above, the ones used for this equation are a bit subjective. The bonus to using this equation is that you can change your dietary target based on periodized changes in your training intensity and total volume week-by-week. However, the caveat with this equation is that it may underestimate caloric needs for sedentary individuals, but I don’t really think that’s the audience at hand. While this is a great equation, it may be more prudent if used by a professional who has a greater grasp on all training and recovery variables; a holistic understanding of the overall program.

TEE/TDEE = Target Body Weight in lbs x (8-11(see below) + total weekly training hours)

For Women or someone less active:

8 - Low Intensity of Training

9 – Moderate Intensity of Training

10 – High Intensity of Training

For Men or someone more active:

9 - Low Intensity of Training

10 – Moderate Intensity of Training

11 – High Intensity of Training

If we wanted to get granular, we could make a step 3 and account for the Thermic Effect of Food (TEF) by multiplying the number we achieved from steps 1 and 2 by 1.05-1.1 (~5-10%), but at that point, we are kind of splitting hairs. The estimated TDEE we calculated through the first two steps is often high enough to account for TEF already. And really at this step, one would most likely be trying to find a way to eat more calories using this multiplier rather than trying to find the appropriate initial caloric intake.

Putting it All Together

Everyone likes examples, it just helps you understand the process better. Here I will use two examples, one male and one female, and set up a scenario so that you can see how things shake out:

Subject 1: Bob “The Bicep” Builder

Age:35

Weight: 200lbs (90.9kg)

Height: 6’0” (182.9cm)

Occupation: Graphic Designer

Training Schedule: Basic weight training 4 days per week (60min sessions)

Body Fat %: Unknown, doesn’t want anyone pinching his love handles

Step 1: Calculating BMR using Mifflin-St Joer Equation:

BMR = (10 x weight in kg (90.9)) + (6.25 x height in cm(182.9)) – (4.92 x age(35)) + 5+

…this broken down is:

(909) + (1,143.1) – (173.3) + 5 = BMR of 1884kcal (calories)

Step 2: Calculating TDEE using an activity factor

TDEE = BMR (1884kcal) x 1.375 (desk job and basic lifting protocol 4 days per week) = 2591kcal

Subject 2: Carrie Crossfit

Age: 29

Weight: 154lbs (70kg)

Height: 5’7” (170.2cm)

Occupation: Medical Sales Representative

Training Schedule: Duh, Crossfit, 6 days per week (60min sessions)

Body Fat%: Using graphic @ 15% body fat

Step 1 using Aragon Equation:

Lean Body Mass = 70kg x .85(take 100 minus 15) = 59.5kg

BMR = 25.3 x LBM (59.5) = 1505kcal

Step 2 Calculating TDEE using an activity factor

TDEE = BMR (1505) x 1.725 (intense exercise 6 days/week) = 2596kcal

Figures 2 and 3. Men and Women Body Fat % Charts (http://legionathletics.com/how-to-calculate-body-fat/)

Legge, A. (2013, October 8). How to Estimate Your Maintenance Calories. Retrieved from https://completehumanperformance.com/2013/10/08/calorie-needs/.

References

Figures 2 and 3. Men and Women Body Fat % Charts (http://legionathletics.com/how-to-calculate-body-fat/)

Legge, A. (2013, October 8). How to Estimate Your Maintenance Calories. Retrieved from https://completehumanperformance.com/2013/10/08/calorie-needs/.