Hydrostatic Weighing: Is it Accurate?

Health and nutrition are changing. While diet and exercise are important cornerstones of better health and fitness, how you create dietary and exercise plans have changed. There are ways to assess your body composition in order to find out how much body fat and lean muscle you are actually carrying, and where. This information allows you to create diets and fitness programs that target specific problem areas for optimal health and wellbeing. Of course, with so many options, it can be hard to know what kind of scans and weight tests are the right ones for you. One option that has been gaining popularity is Hydrostatic Weighing, also known as underwater weighing- but is it really accurate?

What is Hydrostatic Weighing?


Before we can determine whether or not hydrostatic weighing is accurate, we first have to define what it is. Hydrostatic weighing is a type of body composition determination, meaning it measures body fat and lean mass. Using Archimedes Principle of Displacement, hydrostatic weighing measures one's total body density.

The Archimedes Principle states that the buoyant force placed on a submerged object (in this case, you), is equal to the weight of the fluid displaced by the object. Using this principle, the hydrostatic weighing method is believed to determine the percentage of body fat in an individual's body. This is because both the density of fat mass and fat-free mass are constant. On the other end of the spectrum, lean tissues such as muscle and bone are denser than water. With fat being less dense than water and muscle and bone being denser than water, a person who carries more body fat will be lighter underwater, and much more buoyant. A person with more muscle will weigh more underwater and be less buoyant.

In short, this method is designed to give the individual a clear understanding of their body composition: if you are more buoyant, you are carrying more body fat. If you are not, you have more lean muscle.

How is Hydrostatic Weighing Done?

Person underwater

Hydrostatic weighing is a straightforward process with two main components: dry land weighing, and underwater weighing. To execute hydrostatic weighing, the individual is first weighed on dry land. This can be done at home in your personal bathroom or similar space, but it usually is done within the testing facility. Once this is done, the individual will get into a large tank of water. The goal is for there to be enough room for full submersion. Before submersion, however, the individual will sit on a special scale and slowly be lowered into the water. The individual is then asked to remove all the air from their lungs and to remain still while their underwater weight is measured. Overall, the entire procedure is done three times and the results are averaged.

Once the results are tallied, a certain calculation is used to find the lean weight and fat weight in order to reveal the individual's percentage of body fat. This weighing method is considered to be very accurate, but it does come with advantages and disadvantages that can disrupt percentage results and more.  

Pros and Cons of Hydrostatic Weighing

There are a number of components that go into an accurate reading of one's weight and body composition. Due to the variety of moving parts, there is always room for error. Hydrostatic weighing is reported as being more accurate and reliable than most other weighing methods, but it is not all good. These are the major pros and cons of this method of weighing as outlined by Healthfully and Buzzle:


  • The repetition of the of the measurements paired with the reliance on a tried and true principle of density and weight certainly gives it an edge in accuracy.

  • It is a safe option for individuals with pacemakers who cannot undergo electronic weighing methods.


  • Hydrostatic weighing may not be totally accurate for some individuals. Seniors and athletes are at special risk of their body fat percentage being overestimated and underestimated respectively. This is because the body composition of an athlete can be very different from that of an average person, due to their personal muscle mass, fat distribution, and overall fitness level. For the elderly with issues such as osteoporosis, hydrostatic weighing may inaccurately return readings due to the difference in bone composition.

  • Being repeatedly submerged in water is seen as another disadvantage of hydrostatic weighing. Having to go underwater various times without being able to hold your breath before (as the test requires individuals to expel all air from their lungs before they go under), and having to sit completely still can lead to stress and panic for some people. In addition, if the individual moves, retains air, or must be let up before the measurement is finished, the whole test will have to be done again to return the most accurate readings. For some, this is more stress than it is worth.

  • Cost is another major disadvantage of hydrostatic weighing. The equipment used for hydrostatic weighing is incredibly expensive. Unless the individual has access to certain research facilities such as hospitals, colleges, or sports organizations, chances are they won't be able to try this weighing method out without a large out of pocket cost.

  • While this weighing method is considered to be one of the most accurate options, it does not tell you where fat is located in your body. This makes it difficult to know what types of diet and exercise routines are best to target harmful fat, also known as visceral fat.

Though hydrostatic weighing is accurate, it comes with more drawbacks than positives. Fortunately, there is an alternative that gives you all the benefits of hydrostatic weighing, and more: the Dexa (DXA) Scan.

Looking for an Alternative? Try the DXA Scan

On the tails of the hydrostatic weighing method is a revolutionary body composition weighing method known as the Dexa (DXA) Scan. This scan from DexaFit is designed to not just measure the amount of body fat you're carrying, but also tell you where it is in the body. The Dexa Scan is the most accurate method for body composition analysis.  It is approved by the FDA and trusted by elite sports labs and research facilities.

The Dexa Scan is also much simpler than the hydrostatic weighing procedure. All you have to do is pick your appointment location and show up. Once there, you will put on a gown, remove jewelry, and prepare to be scanned by the DXA apparatus. DXA stands for dual X-ray absorptiometry scan. The scan uses two X-ray beams that scan the body for between 10-20 minutes. The scan measures both bone density and full body composition in an easy, non-invasive way. The entire procedure is done in under 30 minutes and afterward, you can return to your normal daily activities.

People tend to enjoy the Dexa Scan more because it is quick, simple, and accurate. When the test is done, you will learn how much body fat you're carrying, where in the body it is hiding, and suggestions for proper dietary and fitness changes to lose this fat and reclaim your ideal body goals.  The Dexa Scan also looks for internal risk factors for health conditions like osteoporosis, weak spots in muscle and bone, and chronic conditions like rheumatoid arthritis, diabetes, thyroid issues, inflammatory bowel disease, liver disease, and much more.

Mountain Yoga

Anyone can use the Dexa Scan, even pregnant women, though DexaFit cautions that you let your physician and the technician know before performing the test. The health benefits from this simple 10-20 minute scan are truly life-changing, making it a great choice if hydrostatic weighing, or other weighing methods, are just not for you. Learn more here.

How To Prepare for a Dexa scan

Human Anatomy

Dexafit is dedicated to providing our customers with the health and wellness tools, benefits, and information they both want and need for their fitness journey. We are always working to push the limits of how you view your body, your fitness, and your health and wellness goals. While we offer many exclusive services that can revolutionize how you exercise and live, one of our most popular services is the Dexa (DXA) Scan. We at Dexafit understand that your body is changing all the time, but you can only tell so much from just looking at the outside. Our Dexa Scan offers you one of the most trusted and accurate methods of finding out whats going on inside your body.

What is a Dexa Scan?

The Dexa (DXA) Scan is an FDA approved procedure that gives you a closer look at your body than you have ever had before. It offers you an advantage in meeting and surpassing your health and weight loss goals while also returning data on how you're doing on the inside. The Dexa Scan is an easy enough process, but it does require some prior preparation. But what exactly is a Dexa Scan? If you're still a little unsure, you are not alone:

The DXA in Dexa Scan stands for Dual X-Ray Absorptiometry. This means that the scan uses two (dual) X-ray beams to scan your body in a thorough yet noninvasive way. Due to this, we can guarantee that the exposure to radiation is low. The DXA Scan itself is brief, taking between 10-20 minutes to completely and accurately test your body composition. The two X-ray beams scan your body from top to bottom, carefully measuring your bone density, muscle composition, as well as the amount of fat you carry and how it is distributed throughout your body. Before undergoing the scan, however, there are a few ways to prepare.  

How to Prepare for Your Dexa Scan

Woman Meditating

One of the best things about the Dexa Scan is that preparing for the procedure is a breeze. The only prior requirement is that you avoid calcium supplements for 24 hours before undergoing the scan. Aside from this, all preparations take place just moments before the scan and are all extremely easy. Many people find the Dexa Scan to be super convenient because it allows them to pop in and out without much hassle. The Dexa Scan itself is quick and simple. All you have to do is show up to the proper Dexafit location at your allotted appointment time, put on a gown, and remove jewelry and any metal objects from your person. Once this has been done, you'll take the scan and be done with the whole procedure in thirty minutes or less. After the scan, most people return to their daily activities without issue.

If you are pregnant, however, be sure to alert your physician as well as the x-ray technologist. Though the scan is safe, there are further adjustments that can be made to minimize exposure and risk to your baby. While you can certainly take the scan while pregnant, we do recommend waiting until after your baby is born, if possible.

What Exactly Does the Scan Do?

The Dexa Scan is designed and used to identify any and all problems, diseases, and conditions in the body. By looking at bone density and body composition, the scan can check for certain diseases like liver disease, rheumatoid arthritis, and osteoporosis before they actually occur. The scan looks for internal warning signs of these diseases that might not show themselves until after its too late, giving you a useful advantage in reclaiming your health before problems develop.

In addition to looking for these diseases, the Dexa Scan can also find weak points in your body. These weak points include areas where muscle mass is thinning or where fractures are more likely to happen. With this knowledge, you can give special attention to these areas to strengthen them and lower the risk of injury.

Finally, the Dexa Scan also measures your body composition. This includes the amount of body fat you carry as well as how and where it is carried in the body. The Dexa Scan returns measurement data on deep belly fat, also known as visceral fat, and can be used to help identify and diagnose certain diseases and health problems like cardiovascular disease, breast cancer, and type-2 diabetes. The scan is so thorough that it will be able to find excess fat between organs, identify problem areas, and determine issues like high cholesterol and metabolic disturbances. With the Dexa Scan, you are really getting a behind-the-scenes look at your body, giving you the knowledge and control you need to prevent health issues, lose weight, and improve your overall fitness.

Results: What You'll Learn and How to Proceed

After the Dexa Scan, your results will return data on your percentage of visceral fat, weak points within the body, warning signs of possible health issues and diseases, and more. This information might be overwhelming at first, but it offers you a comprehensive look at where your body is healthwise.

The results of your Dexa Scan are meant to help you know how much exercise you need, the type of diet you should start, the best ways to build muscle mass, and how to pull your body into the best shape of your life. You can learn how to target specific problem areas of visceral fat, thinning muscle, and brittle bones as well as gain pointers on how to improve fitness and overall health and wellbeing.

Healthy Food

Creating workouts, dietary plans, and wellness goals around the specific needs of your body are important steps for feeling better and living longer. For example, with the help of the Dexa Scan, you can identify the exact location of lean muscle in your body. This information is important because lean muscle plays an important role in the regulation of your metabolism as well as prevents bone thinning and helps prevent chronic diseases and pathologic conditions. Focusing on your muscles and strengthening them also improves blood sugar, sleep, and your balance! When your blood sugar is regulated, your balance is stable, and your sleep is sound and refreshing, you will find that your quality of life improves exponentially. Imagine how much better you can feel and look when you work on improving the different areas indicated in your Dexa Scan results.

Why You Should Get a Dexa Scan


In short, the Dexa Scan has the power to improve your life. This scan offers a simple way to tremendously alter how you view your health and wellness, while also giving you the tools to change how you approach fitness and diet. The scan also helps you to work closely with your doctor about potential issues with your body. By pinpointing and determining problem areas, you and your doctor can make plans prevent and handle any health issues that come your way. With the help of the Dexa Scan, you will always know what's going on with yourself.

Sign Up for Yours Today!

The Dexa Scan is all about the individual. It provides accurate results about your body that help you understand it better than ever. This information is absolutely priceless when it comes to finding ways to improve your health, wellness, and quality of life. If a Dexa Scan sounds like a great idea to you, you can sign up for one today. We have locations from San Francisco, California to Boca Raton, FL, and just about everywhere in between. When you find a location nearest you, you can easily set up an appointment to get your own Dexa Scan done!