A Beginner’s Guide To Body Composition

Which Method Is The Best For Calculating Your Body Composition?

Sections of this article originally appeared on the InBody Blog and is reposted here with permission. To view the original, click here.

We’ve been conditioned to focus on the number on a scale as an indicator of how healthy we are. However, there are actually other body metrics to pay attention to that are a much better indicators of fitness. The main one being body composition.

The Difference Between Body Weight and Body Composition

Both a standard (e.g., bathroom) scale and body composition scale are simple measurement tools. The difference is that a standard scale performs one measurement—your total body weight. A body composition scale breaks down that total body weight into the various elements that make it up.

Your body composition has three main components: fat, lean body mass (muscle, bone, and organs), and water. The percentages of each vary from person to person, by gender (men have more muscle; women more fat) and age (in general as we age we have less muscle mass).

Obviously, as you lose weight, you want to lose fat and not lean body mass. With a regular scale you wouldn’t be able to discover whether you’re on track towards this, but with a body composition scale you can. Most body composition scales will give you the percentage of fat your body weight is made up of. This is very helpful as you lose weight.

Body Composition 101: How To Set Your Goals

What Are the Components of Body Composition?

Body Fat

Having body fat is essential for maintaining body temperature, cushioning joints and protecting internal organs. The energy, or calories, our body needs come from what we eat and drink. You can burn energy through physical activity and general bodily functions. Consuming the same number of calories as you burn means that all the calories are converted into energy. However, if you consume more than you burn, excess calories can store in fat cells. Takeaway: excess body fat comes from energy that did not convert. 

Although you need healthy body fat, too much fat can damage your long-term health. Reducing excess levels of body fat can directly reduce the risk of certain conditions such as high blood pressure, heart disease, type 2 diabetes, and certain cancers.

On the other hand, too little body fat may lead to osteoporosis in later years, irregular periods in women and possible infertility.

Muscle Mass

Muscle mass includes the skeletal muscles, smooth muscles, such as cardiac and digestive muscles, and the water contained in these muscles. Muscles act as an engine in consuming energy.

As your muscle mass increases, the rate at which you burn energy (calories) increases which accelerates your basal metabolic rate (BMR). Therefore, this helps you reduce excess body fat levels and lose weight in a healthy way.

If you are exercising hard your muscle mass will increase, which may lead to increased total body weight. Which is exactly why it’s important to monitor your body composition measurements regularly. So you can see the impact of your training program on your muscle mass and not get a heart attack if your body weight number is higher after a month of hard training.

Water Weight

Body water is an essential part of staying healthy. Over half the body consists of water. It regulates body temperature and helps eliminate waste. You lose water continuously through urine, sweat and breathing, so it’s important to keep replacing it.

The amount of fluid needed every day varies from person to person and is affected by climatic conditions and how much physical activity you undertake. Hydrating yourself helps concentration levels, sports performance and general wellbeing.

Experts recommend that you should drink at least two liters of fluid each day, preferably water. If you are training, it’s important to increase your fluid intake to ensure peak performance at all times.

How Can Knowing Your Body Composition Help?

Body composition analysis is a trending topic in health, medicine, and fitness because it is a whole-body assessment that gives you the blueprint for improving your health.

A standard scale gives only part of the story. Using a body composition scale to measure trends in body fat over time can be a great asset to your weight loss program. This also keeps you motivated and successful!

What Is a Healthy Body Composition?

The American Council on Exercise (ACE) gives these ranges of values for different populations:

Body Composition Fat Percentage

What Effects Your Body Composition?

Influential Factors of Body Composition:

  • Age: People lose muscle mass as they age if they don’t maintain it with sufficient weight training. This results in a slower metabolism.
  • Sex: Women have more body fat than men as nature’s way of preparing for pregnancy and nursing.
  • Genes: These play a role in whether you are naturally lean or have a tendency to retain fat. Including where you store it.
  • Hormones: These can influence water retention and body composition.

What About BMI?

The Centers of Disease Control and Prevention (CDC) has found that while BMI can be used to put people into weight categories, it can’t be used as an indicator of increased health risks. The reason behind this is that it’s not an accurate tool to measure body fatness or assess health because it does not differentiate what your body weight is made up of.

So what does this mean for the average person who is looking to stay healthy?  Well, if you’re simply just that: average (neither athletic nor overweight), then BMI can be a fairly good indicator to measure if you are at a healthy weight.  But if you are even a little bit athletic, or if you lead a fairly sedentary lifestyle, BMI can be misleading.

Example of the Issues With BMI

Take a star NFL tight end. At 6’6”, 262 pounds he would have a BMI of 28.8. According to the World Health Organization, an individual with a BMI score of 30 is classified as “obese.” But you wouldn’t consider him obese  at all when you see him sprint away from NFL defensive backs. The reason his body weight is so high is that more than half of his body weight is made up of muscle.

Although BMI may not be an accurate measurement tool for rich professional athletes, you might be wondering what does this have to do with me.

Read About Why The Shape Index Is A Better

On the flip side, if you are like 150 million American office workers who aren’t getting enough exercise, BMI may be giving you a false sense of security. For example, picture your average office worker as 5’4” and 140 pounds for a BMI score of 23.1: solidly in the “normal” BMI range. This person may want to improve their fitness level, but it’s not a high priority because her BMI is still pretty good.

Sedentary adults working in offices who do not exercise are known to lose Skeletal Muscle mass, especially in their legs. Coupled with a similar increase in body fat   This can lead to high body fat percentages, even in individuals with “normal” body weight and BMI. This condition is called “skinny fat”, and because of our reliance on body weight measurement and BMI, it often goes undetected.

How Can You Measure Your Body Composition?

Skinfold Calipers

This is a method that many people have encountered in their local gym.  Calipers are widely used because they are portable, easy to use, and can be administered by almost anyone. As long as they have had proper training and sufficient experience.

Calipers work by pinching external body fat in several places around your body. Therefore, measuring how much skinfold can be grasped by the caliper’s arms.  Mathematical calculations of the results determine the fat mass in your entire body.


If this sounds simple, that’s because it is.  Calipers are an example of 2C body composition analysis.  Calipers will tell you how much fat you have, but that’s about it.

The other thing to be aware of when you are using calipers to test your body composition is that the accuracy of your results may vary across tests. Also, having consistent test results won’t be as high as tests performed on machines. Which are designed to reduce variance across tests and increase accuracy.

Hydrostatic Weighing


Hydrostatic weighing (also known as underwater weighing) calculates your body fat percentage using you underwater body weight. To get your underwater weight, you first need to expel all of the air in your lungs. Then submerge yourself in a pool while sitting on a special scale.

The next step is to compare your “underwater weight” with what you weigh on land. Then these numbers, together with the value of the density of the water in the pool are put through a series of calculations. Calculations that produce your body fat percentage.

However, just like calipers, hydrostatic weighing cannot report anything beyond body fat, like skeletal muscle mass, body water, and dry lean mass.

Plus getting a hydrostatic weighing test performed is a bit more complicated and not so convenient procedure. You will need to make an appointment at a facility, such as a university or high-end sports complex that has built a hydrostatic weighing pool and a trained staff. And of course you’ll also need to get wet.

Dual Energy X-Ray Absorptiometry (DEXA)

DEXA, is a medical test that involves lying on a table while a machine sends X-rays through your body. It measures the difference in the amount of energy initially going through the body and the amount of energy after it exits the body.

The original use of DEXA was the calculation of bone density. Now DEXA has become useful in calculating body composition. 

For measuring body fat percentage DEXA Scans are the “Gold Standard”.  Unlike calipers and underwater weighing, DEXA scans have the ability to measure the body segmentally. Meaning that it scans each arm and the trunk separately in order to accurately measure fat mass, soft lean mass, and bone density in each segment.

In order to receive a DEXA scan, you will again need to make an appointment with a hospital or clinic that has a DEXA device. You may need to do some research; because of the cost, not all hospitals and clinics will have a DEXA machine.

Bioelectrical Impedance Analysis

Bioelectrical Impedance Analysis (BIA) works by sending a small electrical current into the body. and measuring the opposition of that current (impedance) as it travels throughout the body’s water. Unlike other methods, a technician does not always need to be present at a BIA test, and you can use BIA devices with just by following the directions on the device.

BIA devices range widely in quality and accuracy. You should be aware that not all BIA devices test the entire body.  Consumer body composition scales, use BIA to directly measure leg impedance only and use estimations to determine results for the upper body.  Handheld devices only directly measure arm impedance and estimate results for the lower body.


Because BIA measures work by measuring body water, a lot of useful information can be reported. Nearly all BIA devices will tell you your body fat percentage.

Modern, medical-grade BIA devices are able to measure the entire body directly and can be extremely accurate –  with measurements that are closely aligned with “Gold Standard” procedures – without the complications that those procedures sometimes entail.

The most advanced BIA devices are even able to perform segmental analysis. Because BIA measures work by measuring body water, a lot of useful information can be reported.  Although nearly all BIA devices will tell you your body fat percentage, some devices can go much further and report the body water weight, skeletal muscle mass, lean body mass, and much more.


ShapeScale uses both weight and volume measurements to give a comprehensive and accurate feedback on your overall health & fitness. 

Volume measurements are comparable to under-water weighing, which, as discussed previously, calculates the overall body fat through predictive models. We use similar predictive models to calculate not only your overall, but also localized body fat and lean mass metrics. 

Since ShapeScale is a consumer product, you don’t need any professional assistance to perform your body composition measurements. All you have to do is set up the device in the comfort of your home, step on it and wait for the robotic arm to rotate around your body to complete the scan. A much more convenient and cost-effective solution than most of the previous ones. 

While ShapeScale is less accurate than a DEXA scan or the ‘Golden Standard’, it is far more accurate than regular scales and other conventional 3D body scanners. Additionally due to its depth-sensing and our precise software algorithms, ShapeScale is also unique in its ability of focusing on exact body parts and visualizing your gains and losses. 

All in all, ShapeScale is consumer-friendly, radiation free and completely safe solution for accurate at-home body composition measurement. 

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Lesley George

Lesley is a content writer and community manager at Shape.
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