Many people start a workout program because they want to change the makeup of their body in some visible way. They want to lose weight, gain muscle, increase bone density or decrease inches in certain areas of the body. Their goal is to change their body composition (proportions of fat mass to fat free mass).
Body composition is like the “red-headed stepchild” of the health-related components of fitness. In the overall scheme of things it is incredibly important but it sticks out like a sore thumb.
Four of the health-related components of fitness (cardiovascular fitness, muscular strength, muscular endurance and flexibility) represent things that you do. For example:
- To improve cardiovascular fitness you can run.
- To improve muscular strength you can lift weights.
- To improve muscular endurance you can do push-ups and jumping jacks.
- To improve flexibility you can do yoga.
Body composition isn’t something you do. It’s essentially who you are and the makeup of your body. Although it is different from the other health-related components of fitness, it relies heavily on all the things that you do in relation to them.
What Makes Up the Body?
The body is composed of water, protein, minerals and fat. Using the two compartment model (developed as a way to measure body composition) these components are divided into two groups:
- Fat mass (body fat)
- Fat-free mass
Typically, the greater the proportion of fat free mass to fat mass, the healthier the person is. A healthy amount of fat free mass ranges between 70 to 88 percent for women and 78 to 94 percent for men. In other words, a healthy body fat percentage ranges from 12 to 30 percent for women and 6 to 22 percent for men. Healthy eating practices and regular exercise can help contribute to achieving and maintaining a healthy body fat percentage.
What is Body Fat?
Body fat can fluctuate more than any other type of tissue due to the roles it plays in the human body. They include the following:
- The storage of excess energy (release in the form of free fatty acids into the bloodstream).
- The release of hormones into the bloodstream (used to control metabolism).
- Insulation from the cold.
- Protection for internal organs.
Body fat is stored in different types of fat cells throughout the body.
- Brown fat: Burns white fat when activated and functions more like muscle than white fat.
- White fat: Stores energy and produces hormones that are secreted into the bloodstream.
- Subcutaneous fat: Fat found directly underneath the skin.
- Visceral fat: Fat that wraps around the organs of the body.
Of the different types of fat that make up the body, white fat has the greatest potential for change and accounts for both visible fat gain and fat loss.
What is Fat-Free Mass?
As it relates to the two compartment model, fat-free mass includes all other tissues that make up the body including:
- Connective tissue
All of these tissues call upon the energy stored in fat (if necessary) to function, adapt and change.
Body Composition vs. Body Weight
There is a common misconception that body composition and body weight are interchangeable. This is not the case.
Body weight is an all encompassing measure of the mass of the body (in pounds). Body weight does not differentiate between fat mass and fat-free mass. Body composition is a differentiation and measure (percentage) of fat mass and fat-free mass that make up the body.
This is significant because the density of fat is less than that of fat-free mass.
- Fat mass = 0.9 grams/cm³
- Fat-free tissue = 1.1 grams/cm³
Fat-free mass is more dense than fat mass which means it takes up less space. For example, a person who weighs 150 pounds and has a higher percentage of body fat will take up more space than a person who has a higher percentage of fat-free mass. They weigh the same but their makeup is very different.
Measuring Body Composition
Practical methods of assessing body composition, based on the two compartment model, include:
- Skinfold measurements: Measures the skinfold (subcutaneous fat) thickness of a person at specific sites of the body.
- Bioimpedance analysis (BIA): Measures body composition by sending a low, safe electrical current through the body.
- Hydrostatic weighing (underwater weighing): Measures body density (and resulting body fat percentage) by weighing a person underwater. Hydrostatic weighing is considered the best method for measuring body density and body fat.
Changing your body composition is simple … increase your fat-free mass (primarily muscle) and decrease your fat mass (primarily body fat). The easiest way to accomplish this is to increase your daily physical activity (challenging the other four components of health-related fitness) and making a conscious effort to eat a more balanced diet that does not exceed your daily energy expenditure (Law of Thermodynamics).