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Resting Metabolic Rate--test vs formula

Posted by  blog  Apr 26, 2015

Understanding your Resting Metabolic Rate--The Truth via Testing vs. Fiction via Google

I think at some point in time we have all plugged in our height/weight/age to an online calculator to determine our basic calorie needs for a day. It’s an interesting number and it puts into perspective really what your body is doing when you are sleeping versus when you are active. Most calculators then ask you what level of activity you participate in to give you some bonus calories for effort. Your resting metabolic rate estimates the calories your body needs while at complete rest but not asleep to support breathing, circulation and digestion of food. Your basal metabolic rate is the same minus the calories needed for the digestion of food. Rarely are you at rest that you are not digesting some amount of food so we will speak in terms of resting metabolic rate (RMR).

I did a quick google search for RMR calculators to see where my daily calorie needs would be. The interesting thing was, I entered the same height, weight, and age and got four different answers.  The difference between the four was a span of 200 calories. Well 200 calories a day x 7 days a week, x 365 days in a year is a difference of 73,000 calories or 20.8 pounds! Now that doesn’t take into consideration exercise or strenuousness of your daily routine (job, chasing kids, etc). But still, just the most basic of functions has a huge variability in it based on online calculators.

Now you're probably wondering what your true number is. Let’s look at two examples we experienced during testings at FitnessRx in Louisivlle, KY.  We recently tested two different women who have been struggling with their weight. I got online and calculated her “estimated” RMR from the online calculators. Client A, had a computer generated RMR of 1743 calories per day. So, 1743 calories if she is totally at rest. On her true individual test at FitnessRx, no generalized calculations, just what our ParvoMedics cart captured as her actual calorie expenditure at rest----1440 calories/day. That is a difference of 300 calories a day or 109,500 calories per year or 31 pounds a year. Our second client, Client B, on a computer calculation was 1659 calories/day as her RMR. Her actual RMR, using our metabolic cart, was 1344 calories/day. Again a difference of just over 300 calories!!  So both women had very different basic calorie needs when tested than what the calculator told them…maybe that’s why so many people find those last few pounds difficult to lose.

What does that truly mean though? It means, if you are using MyFitnessPal, Weight Watchers, MyPlate, LiveStrong-anything that you type in your numbers so that it can tell you how many calories a day you need-be aware, it is not as accurate individually as you would you think! Those calculators use typically one of two equations, the Harris-Benedict equation or the Mifflin-St. Jeor equation. They are both reasonable estimators of your calorie needs but if you see that you are struggling to get those additional pounds off, finding your true numbers may be helpful.

The Resting Metabolic/Baseline Activity Test at FitnessRx provides you with not only your RMR but we also have you do two levels of effort on the treadmill (easy then moderate) so that you can get a more accurate calorie expenditure while exercising. Sometimes it is good to have those REAL numbers as well. We also break down for you how many of those calories are carbohydrate calories and how many are fat calories. Most of us have 50,000-80,000 calories stored as fat at any given time. When we exercise, we can train our bodies to use that fat as fuel so these numbers can help you with your calorie expenditure/needs while exercising too.

Contact us today if you would like more information about the RMR/Baseline test. It really is painless-just breathing into a tube and wearing headgear! Let us give you the facts to help you with your health and wellness journey.