What’s Body Composition — and Why’s It Important?


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What’s Body Composition — and Why’s It Important?

Body composition is a term used by health professionals and refers to the percentage of muscle, bone, and fat in your body. Doctors use body composition to determine if you’re at a healthy weight for your body. It’s the most accurate way to track weight loss, muscle growth, and overall health outcomes because total body composition takes a personal approach to fitness.

Body Composition is One of the Five Components of Fitness

Fitness as a whole is often separated academically into five components. These five components are equally important in determining the total fitness of an individual.


  • Muscular endurance is the ability to perform continuous exercises without feeling fatigued. Cycling and step machines help improve muscular endurance.
  • Muscular strength is the amount of force your muscles can produce. This is a total measurement, not a timed test. Improved by the bench press and biceps curl.
  • Cardiovascular endurance studies how the heart and lungs work together to provide oxygen as fuel for sustained workouts. Improved by jogging and swimming.
  • Flexibility is the ability of each joint to move through the available range of motion. Stretching the muscles through yoga or after a workout can improve flexibility.
  • Body composition is the amount of fat mass compared to bone, muscle, and organs. Underwater weighing is the most accurate way of determining body composition.


Total fitness can be defined by how well the body performs in each of the five components. It’s not enough for you to only run a mile. You also need to be able to perform several push-ups.

Why is Body Composition Important?

Body composition is used to find your percentage of body fat compared to non-fat mass, like organs, bone, and muscle. It’s important to figure out fat percentage in this way because a high weight doesn’t always equate to poor health outcomes. For example, a 5’2” and 5’7” woman could both weigh 110 pounds, but only one of those women would be underweight.


Healthier body composition is less fat and more muscle mass, but not so much muscle mass that you don’t have any fat left to protect your organs. Having a high fat percentage puts you more at risk for diabetes, cancer, heart disease, joint problems, and other health issues.


The American Council of Exercise can provide us with an idea of a healthy fat percentage:


Essential Fat10-13%2-5%
ObeseOver 32%Over 25%


You can improve your body composition by gaining lean muscle mass and dieting, but working out is more effective as it replaces the fat and improves your ability to burn calories.

How to Determine Body Composition

To determine your body composition, take one of the following tests. Keep in mind that some tests are more accurate, but you can estimate your fat percentage with online calculators.

Skin Calipers

A skin calliper is a small device that clamps onto your abdomen fat or skinfold thickness since most of your body fat is stored near your waist. It’s possible to receive accurate results from this method, especially from a doctor, but human error is common with skin callipers.

Underwater Weighing

Underwater weighing is the most accurate method of determining total body fat percentage. Since lean tissue sinks and fat floats underwater, weighing machines can separate your tissue to determine your body fat percentage. Unfortunately, It requires specialized equipment.

Dual X-Ray Absorptiometry (DEXA) Scan

Using low-level x-rays, a Dual X-Ray Absorptiometry (DEXA) scan can find how much body fat, bone, and muscle are in your body. It’s primarily used to check for bone density, but trained athletes have started using DEXA scans instead of underwater weighing for quicker results.

Factors Affecting Body Composition

Body composition is influenced by a variety of factors that don’t include diet or exercise. People lose muscle mass as they age if it isn’t actively maintained, and genes play a role in how we retain fat. Hormones can increase water retention at varying intervals, and women have more body fat than men to protect their wombs from damage and to sustain a healthy pregnancy.

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