Metabolism Definition

Metabolism definition, as defined by Wikipedia is “the set of chemical reactions that occur in living organisms in order to maintain life. 

These processes allow organisms to grow and reproduce.

It helps organs maintain their structure and respond to their environment.

What does all this mean? 

To restate this in layman’s terms, the definition of metabolism is the rate that your body burns calories in order to sustain bodily functions. 

The metabolic rate for each person is different and depends on several factors.

Understanding your metabolism and what can impact, is important when trying to lose weight. 

After all, weight loss is all about buring more calories than you consume.

What Impacts Metabolism

Part of understanding metabolism definition is knowing what can impact it. There are certain things that impact your metabolism which you have no control over.  These include age, gender and heredity.


Once you reach the big 40, your metabolism will slow down at a rate of 5% per decade. 

At about the age of 40, your body produces less and less of the growth hormone. 

This hormone is needed for the growing process during childhood and for adulthood to help maintain tissues and organs throughout your life. 

But at around the age of 40 your body begins to reduce the amount of the growth hormone produced.

Once your metabolic rate slows down due to age, you may have to adjust your eating habits by taking in fewer calories than you have in the past as well as add activity. 

Try including both aerobic exercises and strength training in your weekly routine to help maintain and build lean muscles.

man and woman huggingGender

Although this may not seem fair, it is true that men tend to have more lean muscle than women. 

Lean muscle helps to rev up your metabolism.  The reason for this is that muscle is more metabolically demanding than fat.

A healthy range of body fat for women is 20% - 25% and for men the range is 10% - 15% of body fat.  A body fat percent over 30% for women or 20% for men would indicate obesity.


Your genes play a part in your metabolism as well.  Now I don’t mean the jeans you buy at the store, but the genes you got from mom and dad.  Some people are born with a naturally higher or lower metabolism.

If all things were equal between two people; same gender, age, height and weight, and each ate the same amount of calories and got the same amount of exercise, one of these may actually gain weight while the other stayed the same. 

This is because of the different metabolic rate. 

This is where hereditary comes into play.

Determining your basal metabolic rate is not an exact science but most weight loss calculators will be good approximation of your BMR. 

This weight loss calculator not only shows your BMR, but adjusts your calorie intake based on activity level as well. 

When using this calculator, make sure to monitor your progress and adjust as needed. 

You may have a naturally slow metabolism and therefore may have to add more exercise and/or consume fewer calories.

In addition to this article on metabolism definition, read this article on calories definition.

Additional Articles

Calories Burned During Exercise
Rev up your metabolism through exercise.  Learn which exercises burn more calories and how it's calculated.

Metabolism Boosters
Now that you have a good understanding of metabolism definition, check out these methods to boost up your metabolism naturally.

Weight Loss Over 40
Don't let your slowing metabolism slow you down on your weight loss. Check out these tips for losing weight over the age of 40.