What Is Body Composition and Why Is It More Important than BMI? - Step To Health

What Is Body Composition and Why Is It More Important than BMI?

Body composition is a method of analyzing the structure of the body, and differentiates between fat mass, muscle, water, and minerals.
What Is Body Composition and Why Is It More Important than BMI?

Last update: 28 November, 2021

Body composition is a universal term used in the field of health in general. It works to determine the percentage of fat and muscle separately. These can be distributed differently in people of the same size and weight.

Thanks to this more specific delimitation it differs from the body mass index (BMI), which takes into account only the weight and height of the person. Therefore, the latter doesn’t give a very accurate picture of the body’s composition.

Nowadays, the detail of body composition is useful in determining certain health conditions. An abnormal body fat percentage can lead to an increased risk of disease, whether it’s higher or lower. In addition, in weight loss or weight training diets, it allows a more accurate assessment of the results. Would you like to find out more about it? Read on!

What is body composition?

Body composition is a term that’s often used in the medical, sports, and health fields. It refers to the type of mass that makes up each person’s body. This is divided into two main groups; fat mass and fat-free mass.

  • Fat mass refers to adipose tissue. It can be found in different locations, such as in the muscles, under the skin (subcutaneous), or around the organs (visceral fat). A certain amount of fat mass is essential for the body to function properly.
  • Fat-free mass includes all the other components of the body. This includes the bones, organs, fluids, muscles, and tissues. It’s also known as “lean tissue” and is more metabolically active than adipose tissue.

The percentage of fat mass is a measure of body composition that reveals what part of the body is fat and what part is lean tissue. There are ranges that are considered normal and are different for men and women.

What is body composition?
Body composition helps determine the type of mass that makes up a person’s body.

Difference from body mass index (BMI)

Body mass index (BMI) calculates a relationship between weight and height. Because of this, it doesn’t allow us to know what percentage of lipids, muscle and water each individual body has. It’s a very valid marker for diagnosing obesity and excess weight. However, it lacks specificity to assess the degree of adiposity and its distribution.

This is currently a relevant factor, as it’s known that body fat distribution is a determinant for health. For example, abdominal obesity is associated with alterations in blood lipids, inflammation, insulin resistance, hypertension problems, and an increased risk of cardiovascular disease.

Ways to obtain body composition

There are different techniques to determine the amount of fat mass in each person. Some are more accurate than others, and can be implemented at home or in a doctor’s clinic.

Subcutaneous fold measurement

It’s commonly used in weight loss and fitness programs. To carry it out, 6 skinfolds are measured, such as the tricipital, bicipital, scapular, supraspinale, thigh, and calf folds. These measurements are made with a plicometer.

It’s a simple method to implement, inexpensive and minimally invasive. It allows you to estimate the volume of fat stored at the subcutaneous level, which can be correlated with total body fat.

Bioelectrical impedance

This technique uses small devices or scales that pass an electric current through the body. These measure weight and other variables such as fat, water and bone tissue. Some of them are for home use and quite easy to interpret.

Underwater weighing

This is the optimal way to measure a person’s body composition. However, it’s one of the most difficult to perform as it involves submerging the individual in a tank of water.


This is an absorptiometry scan performed through exposure to X-rays. One of its advantages is that it accurately determines bone density.

How to maintain a healthy body composition

Some ranges of fat mass are considered normal, and are different according to the sex and age of the person. As can be seen in the American Journal of Clinical Nutrition the following are the ranges:

  • 20-39 years: 21-32% in women and 8-19% in men.
  • 40-59 years: 23-33% in women and 11-21% in men.
  • From 60 to 79 years: 24-35% in women and 13-24% in men.

Body composition is partly determined by genetics. Despite this, some factors can help to modify it. Without going into specific cases, here are some positive lifestyle habits to maintain a healthy body composition.

Being physically active

Staying active is a crucial way to increase calorie expenditure and prevent fat accumulation. A simple way to achieve this goal is to climb stairs and walk whenever possible.

Include resistance exercises in your routine

This type of training is the most appropriate when you are looking to boost muscle growth. In addition, other exercises can be implemented to help decrease accumulated fat.

A woman doing weights.
Resistance exercises enhance fat loss and help muscle mass growth.

Consider calories

Both for obesity prevention and to promote the development of muscle mass. Eating more or less, depending on each person’s needs, can lead to changes in fat and lean mass percentages.

Maintain a good quality diet

To improve body composition and overall health, it’s imperative to avoid fast food and most processed food as much as possible.

Ensure protein intake

This is one of the key nutrients for the development of muscle mass. Even if a weight loss diet is to be followed, it helps to increase the feeling of satiety.

Set long-term goals

Achieving the right body composition isn’t impossible, but it isn’t immediate either. For this reason, you should be wary of programs that promise quick results. In fact, you need to keep working once you have achieved your goal.

Drink enough water throughout the day

Fluid intake throughout the day correlates with body water percentage. In general, it seems that the higher the intake, the better the body composition. Incidentally, it could be useful in the prevention of excess weight and obesity.

In contrast, the presence of alcohol seems to influence in the opposite direction. All the extra energy consumed in the form of alcohol is stored as fat. Also, drinking alcoholic beverages is associated with increased food consumption.

Improve sleep quality

Several scientific studies show that people who have poorer sleep quality also have poorer body composition. However, the exact causal relationship isn’t yet clear.

Body composition is a good indicator of health status

Body composition is unique for each person, independent of weight and height. It can be measured by different methods and, unlike the body mass index, gives a more detailed picture of how a body is structured.

The importance of this detailed “portrait” goes beyond an aesthetic issue. In particular, it plays an important role as a determinant of health and, in fact, can predict the risk of certain diseases.

Excess body fat is often associated with an increased risk of cardiovascular disease. On the other hand, muscle mass is essential to ensure mobility, body posture, and a better quality of life in old age.

There are some habits that allow us to maintain a healthy body composition. Even so, it’s necessary to take into account that each person’s starting point and objectives may be different. For this reason, it’s advisable to consult a specialist in order to draw up an individual plan, whether the percentage of fat is above or below advisable levels.

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