What is metabolism? In simple terms it’s all the work your cells do to keep your body alive and thriving. Sit with this for a moment, and imagine the trillions of cells that make up your body, all of them burning bright with potential energy. If your cells could shine, all of them together would burn brighter than a star! You are a walking powerhouse of potential with a trillion possibilities! You. Are. Amazing.

Your body is such an extraordinary machine, it deserves to be treated with awe and respect. This means keeping it fit, feeding it the nutrients it needs to thrive, making sure it gets proper recovery in the form of sleep and stress management. If you are not doing these things for your body, what does it owe you?

Ok getting down off my high-horse, let’s talk numbers. Unless you are getting your metabolic rate measured in a lab, you can find some reasonable numbers on your own with the help of a few equations, and like with any scientific theory, some trial and error.

This chart is one that I use, it is very basic but gives a pretty close approximation your energy needs for each type of day, including your daily activity (unless your activity levels are much much higher as in a professional athlete, or you have a veeeery physically active job). This is your metabolic rate, or the amount of energy your body burns in one day.

You can also use multiple equations to find your Resting (Basil) Metabolic Rate, which is what your body is burning at rest, before adding in your daily activity rate. I like the Mifflin St. Jeor equation which is the next figure shown.

I am 45 years old, 5’3” and weigh around 120lbs. My body’s RMR is (according to the Mifflin St. Jeor equation) just under 1200 with an added 233 Kcal for “light” activity bringing me to a total of just under 1400 Kcal for a non-training day. Now, from experience, this amount of energy input is too low for me since I tend to have a step count over 10K/day, so I naturally bump it up to 1500 kcal for a non-training day (which is right on target in our first chart above).

On light activity days, like a hike, lots of walking or easy aerobic work under two hours, I will eat around 1650-1700 Kcal and feel full and light all day. A moderate activity day would be strength training under 1 hour, moderate-level ride or run, plus my added steps and I easily more in the range of 1900 Kcal/day! And of course, on a hard training day of strenuous movement lasting more than 90m-2hours I would eat in the range of 2100 Kcal (these days are few and far between).

What does all of this have to do with my metabolic rate? More than you think! Stay tuned to find out how we can use this information to improve our health and body composition!

Now, remember in my last post, I mentioned your body works hard to keep your metabolic rate within a narrow range (similar to your body temperature, pH, etc.). This means (are you ready for it?) that no matter how much exercise or movement you get, your body is burning roughly the same amount of energy (calories), and there is only so much energy that your body can produce before it begins to impact other systems negatively.

Now, the caveat to this is those damn activity trackers… they will tell me that I “burned” 3500 kcal today and so makes me believe that I can go ahead and EAT 3500 kcal worth of nutrients to fill the deficit. In truth, this would only happen the first few times I had such days, because don’t forget, the body wants to keep the metabolic rate within a narrow range. So If I am “burning 3500 kcal” during one day, that energy need is being pulled from other areas of my metabolism, like the immune system, reproductive system, etc. so if I forget that my body is accommodating in other ways, and I go ahead and just eat what I believe I burned that day, I am going to eventually be eating in a calorie surplus, and I am going to gain weight. (There is the flip side to this argument as well, if you do not eat enough to support your BMR, your body will sloooow way down and preserve it’s fat stores and you will hold onto or even gain weight as well).

WOW. A lot of information. What do we do with this? There is a simple way (I said simple, not easy) to work with your body’s amazing metabolic prowess. Stay tuned for more geeky information this week!