Understanding Metabolism & Its Components

Do U understand your metabolism? Chances are you don't, from the looks of this amazing in-depth article from Justin Janoska!

If you have a minute or two, it just might change your health-life forever. Take a look:

Most of us have heard and used the term “metabolism” and have used it in the context of “I have a fast/slow metabolism,” but what does that really mean? We assume that if someone is lean and muscular that they must have a “fast metabolism” and vice versa. In reality, to say someone has a “fast metabolism” means that person has a multitude of physiological processes occurring such as digestion, respiration, circulation, activity, growth, etc. This makes sense since metabolism is defined as the sum of all the actions in the body to sustain life. Conversely, if someone were said to have a “slow metabolism,” this would correlate with slower metabolic processes, less movement and less muscle tissue.

Metabolism can be divided into 5 constituents:

The BMR or Basal Metabolic Rate accounts for 75% of the body’s daily expenditure and includes an obvious major part of physiological functions. Specifically, it is the lowest amount of energy needed to sustain life without movement, digestion or anything other than basically breathing. Due to these specific controlled environmental conditions that involve a measure of oxygen exchange, it is very difficult and unrealistic for most people to have their BMR measured.

Your RMR or Resting Metabolic Rate is often used interchangeably with BMR because they virtually represent the same thing. However, technically RMR includes digestion and movement. Thus, RMR is roughly 10% higher than the BMR.

When we are interested in determining our daily estimated energy expenditure, we often see formulas use BMR or RMR. There are several formulas out there, but according to the research, the Mifflin equation (see below) has been shown to be the most accurate in calculating your RMR, especially in non-obese populations. Yet, your caloric prediction can be off by +/- 10%.

RMR = 10 (weight in kilograms) + 6.25 (height in centimeters) – 5 (age in years) + 5

For example, if you are a 16 year-old female who weighs 110 lbs. and is 5 feet and 6 inches tall, the amount of calories you need daily without exercise is approximately 1,470.

Next you would use one of the following multipliers to ultimately find the amount of calories required to maintain your weight.

RMR x 1.2 if you do not exercise
RMR x 1.375 if you perform light exercise 1-3 times a week
RMR x 1.55 if you perform moderate exercise 3-5 days a week
RMR x 1.725 if you perform hard exercise 6-7 days a week
RMR x 1.9 if you perform intense daily exercise

So, if our 16 year-old female exercises 1-3 times a week, her baseline or caloric needs for the day would be about 2,021 (1,470 x 1.375).

Using one of the multipliers above gives a rough approximation of the energy expended for the given exercise in addition to your RMR. Since it is not entirely accurate, using another method that reflects the specific activity performed would be more realistic.

If our 16 year-old female had the goal of losing weight, she would take in a slightly lower amount of calories. Somewhere between 1521-1721 calories per day would put her between 300-500 calories below her baseline of 2,021 and establish the deficit needed to lose weight.

The Thermic Effect of Food or thermogenesis incorporates the processes of food digestion, assimilation, absorption and heat production in the body. So, when we eat our metabolism rises and this represents approximately 10% of our daily expenditure. It is frequently factored into the energy expenditure equations. A common misconception is that eating more often will cause this number to increase. Unfortunately, this is not the case. Whether you decide to eat twice a day versus 8 times a day, there appears to be no significant difference total energy expenditure or enhancement of thermogenesis.

It goes without saying that exercise can make a huge impact on your daily caloric needs. This is a variable that differs from person to person and reflects the type, duration and intensity of a specific activity. For sedentary people, this factor can be as low as 10% of their daily expenditure and more than 30% for those who are very physically active. Additionally, EPOC or excess post-exercise oxygen consumption can become a large factor that increases metabolism after exercise due to the energy deficit created during exercise.

NEAT or Non-Exercise Activity Thermogenesis comprises the last part of metabolism. It is also referred to as incidental exercise due to the low intensity, impulsive, casual activity that you perform daily such as picking something up, fidgeting, stretching, etc. Since it accounts for a very small part of metabolism, this energy expenditure is typically represented by the factor previously mentioned, physical exercise.

Hopefully, you now have a better understanding metabolism, how it works and what it comprises of when you calculate your daily caloric needs. Remember to factor in the calories expended from exercise and add it to your RMR whether it is by using the multiplier or another method. This will then give you the total amount of calories needed to maintain your weight for the day.

Justin just so happens to be a passionate fitness trainer certified by NASM, as well as a sports & exercise nutritionist, and would love to hear from you on Twitter & Facebook! Make sure you check out his website HERE… and if U wanna know more about metabolism OR anything else, U can always email us at Questions@FitPerez.com!!

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