Your body is constantly using energy. Your body uses energy to perform the most basic tasks, like breathing, circulating blood or your basic brain functions. All of these uses of energy are what we consider as your body's resting metabolism. Knowing your individual RMR (Resting Metabolic Rate) is essential to finding out how many calories you should be eating on a day to day basis. Knowing how much you should be eating daily to maintain your ideal weight is important to determine how much you should be eating to lose weight.
Since we’re all different, we all have a different RMRs (Resting Metabolic Rate). Your RMR is an estimate of how many calories you'd burn if you were to do absolutely nothing but rest for 24 hours. But how do you figure out YOUR RMR? Well, before we do so, it’s important that you understand what influences your RMR:
- Calories burned via activity/exercise.
- Digestion (thermic effect of food).
- Calories burned via non-exercise activity.
How to calculate you your RMR
The first thing to do is to figure out your LBM (Lean Body Mass). Take your overall body weight and subtract your body fat from that number. To obtain your body fat, I recommend using calipers as shown in this video here.
Why do we need to measure body fat?
Your muscle require more energy than body fat to work correctly. Although two women may weigh the same exact scale number, their body composition may be completely different resulting in two very different RMRs.
Now that you know your estimated body fat percentage, let’s take that number and figure out your LBM (Lean Body Mass) so we can plug it into the Katch Mcardle formula (which helps to calculate your BMR; basal metabolic rate).
Now, let’s say your 140lb and have a body fat of 28%. To figure out your lean body mass, (LBM), calculate
(1- .YOUR BF PERCENTAGE) x YOUR WEIGHT = LBM
Which would look like: 1-.28 x 140 = 100
Let’s say hypothetically these are your numbers, This would mean your LBM is 100lbs. Now we can plug this number into the Katch Mcardle formula.
The Katch Mcardle formula is: BMR= 370 + (9.82 X Lean body Mass)
That would look like this: 370 + (9.82 x 100) = 1352
Now, depending on your activity level, the final number to multiply your BMR with varies depending on how active you are. The variation can be anywhere from 1.25-1.9.
- Sedentary = BMR X 1.2 (little or no exercise, desk job)
- Lightly Active = BMR X 1.375 (light exercise/sports 1-3 days/wk)
- Moderately Active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)
- Very Active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)
- Extremely Active = BMR X 1.9 (hard daily exercise/sports & physical job or 2 X day training, full time training, etc.)
For most of my clients who have office jobs and are stay at home moms, I use 1.3-1.5 but consider your own daily energy expenditure.
Let’s use 1.3 for hypothetical reasons. Here’s what that would look like:
1352 x 1.3 = 1757 is the number of calories you need to maintain on a daily basis.
From here, you would just need to subtract anywhere from 300-500 calories from your RMR.
Keep in mind, with all these measurements and calculations, nothing is exact. We are talking about an estimate of calorie maintenance, but as long as we are close to your individual estimates, we will get you to see some kind of results. At the very least, no matter who you are and what your goals are, making sure you are hitting your individual RMR will ensure your body and mind are functioning at its most optimal level.
Looking to calculate your LBM and RMR?