This word “metabolism” is thrown around a lot these days.
How many times have you or someone you know said:
“I just have a slow metabolism.”
“She’s so lucky, she must have a super fast metabolism.”
“My metabolism has slowed down now that I’m older.”
But what exactly does this all mean?
Well technically “metabolism” is the word to describe all of the biochemical reactions in your body. So fancy right? It's how you take in nutrients and oxygen and use them to fuel everything you do.
Your body has an incredible ability to grow, heal, and generally stay alive (FYI that is it’s sole purpose). And without this amazing biochemistry living would basically be impossible.
Metabolism includes how the cells in your body:
So when you put all of these processes together into your metabolism you can imagine that these processes can work too quickly, too slowly, or just right.
Much like Goldilocks and the Three Bears! ;)
Which brings us to the “metabolic rate”.
This is how fast your metabolism works and is measured in calories (yup, those pesky calories!).
The calories you eat can go to one of three places:
As you can imagine the more calories you burn as work or creating heat the easier it is to lose weight and keep it off because there will be fewer “leftover” calories to store for later.
Remember though that it’s not as simple as just tracking calories for fat loss.
There are a couple of different ways to measure metabolic rate. One is the “resting metabolic rate” (RMR) which is how much energy your body uses when you're not being physically active.
The other is the “total daily energy expenditure” (TDEE) which measures both the resting metabolic rate as well as the energy used for “work” (e.g. exercise) throughout a 24-hour period.
Both of these numbers can be vastly different from person to person and online calculators only give you an average guesstimate of what yours MIGHT be, which is why calorie counting alone is not the best approach for fat loss.
What affects your metabolic rate?
In a nutshell: A lot!
1. Your thyroid.
This gland at the front of your throat releases hormones to tell your body to “speed up” your metabolism. Of course, the more thyroid hormone there is the faster things will work and the more calories you'll burn.
Now this doesn’t mean you become a thyroid pill popper but it does mean that you should get a full thyroid panel to make sure yours is functioning properly. Just do me a favor and don’t only see your general doctor, he/she will may not run all of the proper tests.
But your thyroid isn’t the only thing that affects your metabolic rate. How big you are and your stress level influences it too!
2. Size matters.
Larger people have higher metabolic rates but to be clear, body composition relative to size matters.
3. Muscle mass.
As you can imagine muscles that actively move and do work need more energy than fat does. So the more lean muscle mass you have the more energy your body will burn and the higher your metabolic rate will be. Even when you're not working out.
This is exactly why weight training is often recommended as a part of a fat loss program. Because you want muscles to be burning those calories for you.
The thing is, when people lose weight their metabolic rate often slows down which you don't want to happen. You definitely want to offset that with more muscle mass. Lift the heavy things ladies!
I hate to say it. I mean you know my feelings for cardio. But aerobic exercise also temporarily increases your metabolic rate. Your muscles are burning fuel to move so they're doing “work”.
But don’t miss that word “temporarily”. Why it may work in the moment, it does not have the same effect muscle mass has long term.
5. Type of food you eat.
Your body actually burns calories to absorb, digest, and metabolize your food. This is called the “thermic effect of food” (TEF).
You can use it to your advantage when you understand how your body metabolizes foods differently.
Fats, for example increase your TEF by 0-3%; carbs increase it by 5-10%, and protein increases it by 15-30%. By trading some of your fat or carbs for lean protein you can slightly increase your metabolic rate.
Eat more protein. Hmmm...where have I heard that before??
Another bonus of protein is that your muscles need it to grow. By working them out and feeding them what they need they will help you to lose body fat and keep it off.
This is just the tip of the iceberg when it comes to metabolism and how so many different things can work to increase (or decrease) your metabolic rate.
I am a wife, mom, grandma & former professional “diet and exercise hopper" who understands the challenges of being 40lb overweight after having children & the damage repeated sense of failure can cause to your confidence and self-esteem.