“Metabolism” is thrown around a lot. You know that yours might be too slow if you are gaining or holding on to extra weight. But what exactly is metabolism?

Technically, “metabolism” is the word that describes ALL the biomechanical reactions in your body. It’s how you take nutrients and oxygen and use them to fuel everything you do.  Your body has an incredible ability to grow, heal and function. And without this biochemistry you wouldn’t survive.

Metabolism includes how your cells allow:

  • Activities you can control (i.e. physical activity)
  • Activities you can’t control (i.e. heart beat, wound healing, processing of nutrients and toxins, etc.)
  • Storage of excess energy for later.

So when you put all these processes together into your metabolism, you can imagine that these can work too quickly, too slowly or just right.

Metabolic Rate

This is how fast your metabolism works and is measured in calories. The calories you eat can go to one of 3 places:

  • Work (i.e. exercise and other activity)
  • Heat (i.e. from all those biochemical reactions)
  • Storage (i.e. leftover calories stored as fat)

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.

So how do you measure metabolic rate? One way is the resting metabolic rate (RMR), which is how much energy your body uses when you’re not being physical active. This is also sometimes also referred to as basal metabolic rate (BMR). This is what your body uses just to function enough to keep your organs going through those biochemical reactions.

The second way is the total daily energy expenditure (TDEE), which measures both the resting metabolic rate AND the energy the energy used for work throughout a 24-hour period.

What affects metabolic rate?

Well….A LOT!

The first thing you may think of is 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.

But your size plays a role as well. Larger people have higher metabolic rates; but body composition (% lean muscles vs. fat) plays a critical role as well. You’ve probably heard that muscle burns more calories than fat. That’s because muscles actively move and do “work”; therefore, they 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 exercising.

This is one of the reasons why weight training is so important and is often recommended as a part of a weight loss program. You want muscles to be burning those calories for you.

And as you lose weight, you want the muscle gains to offset the slowdown in metabolism from an overall decrease in size that comes with weight loss.

Aerobic exercise (think cardio) also temporarily increases your metabolic rate. Your muscles are burning fuel to move so they are doing “work”.

The type of food you eat also affects metabolic rate. Your body burns calories to absorb, digest and metabolize your food. This is called the thermic effect of food (TEF). You can use this to your advantage when you understand how your body metabolizes different foods.

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.

And another bonus of protein is that your muscles need it to grow. By exercising them and feeding them what they need, they will help you lose weight and keep it off.

And don’t forget the mind-body connection. There is plenty of research that shows the influence that things like stress and sleep have on metabolic rate.

This is just the tip of the iceberg when it comes to metabolism and the number of things that can work to increase, or decrease, your metabolic rate.


What do you believe about your metabolism?