Energy In vs Energy Out

In our everyday discussions about diet and exercise, we throw the word “metabolism” around very casually.  But I feel like the word “metabolism” is like the word “irony” in that we all kinda know what it is but we can’t define it.

So what is our “metabolism?”  With scientific specificity, it refers to both the anabolic and catabolic reactions in our bodies.  In layman’s terms, I like to think of our “metabolism” as being all the energy that our body exerts to do all that it can do.  Generally, our daily metabolic rate (the rate at which our metabolism works (or) the number of calories/amount of energy our bodies need to sustain it’s normal daily function) is also called our total energy expenditure.  This total daily number is broken down into a few specific parts which make up the whole.

(1)  BMR (basal metabolic rate) or RMR (resting metabolic rate).

This number refers to the amount of energy that you exert when you’re resting.  This means you’re not eating or haven’t just eaten (your digestive system is not in use at the moment) and you’re not exercising.  In all, it refers to the energy that your essential organs exert to sustain it’s normal functions.  Think…heart, lungs, brain, skin, etc.

(2) TEF (thermic effect of food).

This is our favorite number!  It’s the amount of energy our body uses when digesting food.  That includes the mechanical and absorption portions of digestion.

(3) PAL (physical activity level).

Aside from our resting energy and thermic effect of food, we also account for our physical activity.  Here, you can include exercise or just normal moving around.  The more you move/exercise, the higher this number.  Generally, we relate this to our daily workout and how many calories we just “burned!”

When you put all of these together you get a good estimate of your total energy expenditure (TEE) for each day.  It’s important to know this because it relates to how many calories you need to eat.  Remember, the TEE is the energy OUT portion of the equation; you have to control the energy IN portion via your diet.

Download the “MyFitnessPal” app or simply go to their website ( and it will help you estimate the number of calories you need to sustain your weight each day.  The best part of the app (aside from it being free) is that it has a great food diary component that helps you keep track of what you eat and if you exercise.  It helps to account all of that information into your daily diary.  Some people actually use a food diary every day and have done so for years now.  That is how it works for them.  But you don’t have to do it for years; you can still benefit from doing it for a few days to literally see how much your eating and how much your exercising (or not). You will definitely be surprised, so try it out for a week!

And that’s your metabolism in a nutshell



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