Metabolism 101

katiechang116
Mar 9, 2017
3 min read

Me·tab·o·lism

noun:

"the sum of the physical and chemical processes in an organism by which its material substance is produced, maintained, and destroyed, and by which energy is made available." (1)

We all are familiar with the term "metabolism". It means many things to people. We talk about boosting our metabolism or revving it up. All you have to do is google metabolism to find the latest diet that can supposedly increase your metabolism and help you shed pounds. What people may not ask is why they have a "slow" metabolism or how to support their metabolism so it remains strong.

First off, let's start with an understanding about what exactly our metabolism is. As the definition at the beginning of this blog states, metabolism describes any and all processes in our bodies that make energy available. Calories are a unit of heat that is used to create energy in our body. That is why people think of calories when they talk about metabolism.

Our metabolism can be understand in terms of a rate or speed of energy usage. We use energy (i.e. calories) to create useable energy our body (i.e. ATP). The sum of our metabolic rate is called the total metabolic rate (TMR). There are three main components that make up our TMR. These include our basal metabolic rate (BMR), the amount of movement or physical activity we engage in, and the thermogenic effect of consuming food (TEF). Below is a graph depicting the percentages that these components make up in our TMR.

As you can see from the graph, our BMR makes up the largest component of the metabolic rate. Researchers in the 80's found that our BMR makes up anywhere from 56-80% of our TMR (2). Physical activity makes up ~10% and the final 10% goes to the thermic effect of food (TEF).

Okay, so now that we know the three main components of our metabolism what exactly are they?

The BMR is the rate of energy expenditure at rest (3). It can vary widely in an individual based on a number of components. Some in our control and some out of our control. These factors include:

Age: After our 20s, our BMR decreases by 2% each decade.
Gender: Men tend to have greater muscle mass, which is more metabolically active than fat tissue. As a result, men have a higher BMR.
Thyroid hormones: Adequate T3 (the active thyroid hormone) is essential for maintaining a "normal" BMR.
Body Composition: Again muscle is more metabolically active at rest than fat tissue so someone with greater muscle mass will have a higher BMR.
Weight: The greater the amount of body weight the higher the BMR.
Surface area: Taller people have a higher BMR as they have more surface area on their body.
Other factors that contribute to the BMR include one's genes and medications.

Physical activity or movement is pretty self-explanatory. If you are physically active you are expending more energy, thereby increasing your metabolic rate. However, as the graph suggests, physical activity makes up a small percentage of your TMR.

If you have ever worked out on a machine that tells you how many calories you "burned" you may have already discovered this. After a 30-60 minute workout it can be shocking to find out that you only "burned" 300-500 calories. After you leave the gym and eat your protein bar (around 200 calories) you realize that while physical activity is vitally important it does not result in a major calorie deficit like you thought. However, long-term physical activity can lead to an increase in muscle mass, which can increase one's TMR.

The last component of the TMR is the thermic effect of food (TEF). Again, this has just a small effect on your metabolism. TEF is the amount of energy required to breakdown and digest food. If you eat smaller, more frequent meals you experience a slight boost to your metabolism because each time you eat it requires some energy. This is why so many dietitians encourage people to eat 4-6 small meals/day rather than 1-2 large meals.

Now before you take this information and try to use it as your next solution to lose weight consider this. Dieting and severe calorie restriction can reduce one's BMR by up to 30% (2). In my next blog I will explain why this phenomenon occurs as well as discuss ways to normalize your metabolic rate after a history of chronic dieting. Stay tuned and feel free to leave a comment below. If you are ready to take action and get help as you work to improve your metabolic function set up an appointment using the link below.

https://katie-chang.clientsecure.me/client_portal

Warmly,

Katie Chang