Metabolism: what it is and how to make it more efficient

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By Jen Pfeifler LD, Ms | Just. Love. Pears. nutrition | Updated: January 2025

Metabolism. What comes to mind when you think about this commonly thrown around term? How much can I eat before it affects my weight? Does it slow down the older I get? Or maybe how quickly do I burn food?

This article was inspired after a conversation with a family member who has been diagnosed with a condition called collagenous colitis. The cause is unknown, but involves chronic inflammation of the large intestine or colon. As a result, multiple bouts of urgent daily bathroom trips are now part of life. As you can imagine this has caused some unfavorable consequences!

When I got a phone call asking: "Hey Jen, all these trips to the bathroom just mean I have fast metabolism, right?" I thought it might be a good idea to break this down a little further!

Although I can see how someone might come to that conclusion, let me explain what metabolism is and what it is comprised of.

Metabolism simply put, is the chemical reactions that occur in a living organism that sustains life. Basically, it is made up of 3 factors plus your hardwired genetics. I like to remember it by saying Metabolism = 3 + HG. So all added up metabolism = some modifiable factors (behaviors you can change) + some non-modifiable factors (the deck of cards you were handed at the start this crazy life). Let's take a deeper dive into the chemical processes:

1) Resting Metabolic Rate (RMR) - This is how much energy you burn while at rest. This does not include the exercise or movement you do throughout the day. Not even walking to and from the mailbox. It takes approximately 1600-2500 Kcal just to function a human being! So the saying, you have to work for your food, or needing to restrict to make up for the dinner you are going to have later tonight is just plain inaccurate- and quite frankly a really negative mindset to be in. Food is necessary. Always remember that. You have permission to never apologize for eating. EVER.

2) Physical Activity Level (PAL) - This is as straight forward as it sounds. Now is the time you can account for the mailbox trip. This also includes any structured exercise at the gym, or walking/hiking/cycling you do outside. This is really all the movement you do throughout your day. It takes energy to get that body moving! The more efficient you are at the movement (becoming faster at running a mile or becoming quicker at climbing up a flight of stairs) the less energy it requires. You may have heard of the term "rookie gains". This term comes from the body having to go from 0 to 100, meaning your strength/fitness improves significantly over a short period of time. The fitter/faster you are, the more effort it takes to get just a small amount of "gains". Think of the Olympic 800 meter runners- to beat their time by a fraction of a second takes years of training, and probably some help from the wind! I do want to point out, you do NOT have to slay yourself at the gym or run a marathon to achieve health benefits. Halleluiah!

3) Thermic effect of Food - This means how much energy it takes to absorb nutrients and drive energy to where it needs to go (ie brain, muscles, cells). Not something you would think of, right?! So maybe a correct analogy is to think of a car starting. To start the car and put it in drive, takes fuel. You haven't even moved, yet you're an energy burning machine!

Metabolism is made up of a few different factors, all varying in efficiency depending on the individual. Nutrition plays a huge role in determining that efficiency.

Hands down the easiest switch you can make right now

Eating breakfast is probably the easiest change you could make starting tomorrow that will help to get your body burning and set your day for productivity and energy. Eating enough is the next step and in my experience the most difficult.

Need help to increase your metabolism? book online or send me an email at jen@justlovepears.com to learn more about what I can do for you. Check out my podcast I co-host, How to eat cake_the pod for some fun discussion on diet culture and how to get out of the diet and weight loss trap!