Hydrostatic Weighing
What is Hydrostatic Weighing?
Hydrostatic Weighing is a fast and accurate method of measuring body composition. A standard Hydrostatic Weighing test with a Fitnescity partner involves sitting on a specialized scale while being submerged underwater to calculate fat and lean mass, lung volume, and body density.
Most people are used to stepping on a scale now and then. But monitoring weight – while helpful – is not a precise way of assessing wellness or fitness. Body composition measurement with Hydrostatic Weighing can look beyond weight and the traditional body mass index (BMI) to determine body composition.
How does Hydrostatic Weighing work?
Hydrostatic weighing is one of the most accurate ways to measure body fat percentage, and was the most popular method of body composition measurement among athletes until more sophisticated scanning technology emerged.
The Technology
Hydrostatic Weighing is a method of body composition measurement which uses body density and Archimedes’ Principle of Displacement to determine how much fat and fat-free mass a person has. Wearing a bathing suit, the test subject is first weighed on dry land and then, while sitting on a special scale, the subject will exhale all the air from their lungs and be lowered into a tank of water until completely submerged. This will be repeated several times for precision.
Archimedes’ Principle of Displacement states that a body at rest underwater is acted upon by buoyant (upward) force equal to the weight of water displaced by the body. The volume of water displaced is equal to the volume of the object. By measuring a Hydrostatic Weighing subject’s weight on land and underwater, body density can be calculated. Because different composites of the body have different, but constant, densities, a heavier underwater weight indicates more fat-free mass and a lighter underwater weight indicates more fat mass. Using specialized calculations, fat and fat-free mass weight and percentage can be derived.
Your Appointment
What happens during a Hydrostatic Weighing test? You will arrive to the test center 15 minutes prior to your appointment having followed the proper pre-test protocols. The location may have you sign additional paperwork before taking you back to the weighing tank. After putting on your bathing suit & swim cap, the test administrator will collect your weight from a scale on dry land and help you to sit comfortably on a specialized scale. You will be lowered into the tank of water until completely submerged and expel all the air from your lungs before being raised. This process will be repeated 2-3 times to ensure accuracy.**
What are the benefits of Hydrostatic Weighing?
Whether your goal is to lose, gain, or maintain weight, hydrostatic weighing provides body fat analysis including fat mass and fat-free mass. Knowing this information about your body is crucial for optimizing your wellness, preventing disease, and tracking change over time. Most people are accustomed to stepping on a bathroom scale every now and then, but monitoring weight – while helpful – is not a precise method of assessing wellness or fitness.
Look beyond the bathroom scale.
Have you ever been surprised or frustrated by your weight after starting a new training plan or diet? This is not unusual, as most people do not fully understand the daily fluctuations that happen in the body or what factors can impact weight. Hydrostatic weighing is a great monitoring tool because it allows you to see how much fat and not-fat mass you have and how their ratio is changing. Sometimes, when in a caloric deficit or when macronutrient intake is unbalanced, the body can actually draw energy from muscle mass rather than fat stores during exercise. Regular hydrostatic weighing tests can help ensure you are gaining or losing mass the way you want to and help you stay on track for your goals.
A hydrostatic weighing test can be completed in a few minutes, and provides highly accurate, safe, and fast test results. It is also non-invasive, making it especially suitable for frequent, longitudinal tracking of body composition and metabolic changes over time.
BMI vs. Body Fat Percentage
BMI is one of the most popular methods of determining how healthy one’s weight is for their height. However, this method has numerous failings. The body is comprised of different substances which decrease in density from bone (the most dense) to fat (the least dense) with muscle in-between. Combinations of different substances can result in similar weights despite drastically different body compositions. For example, a lean individual with high muscle mass can weigh the same as an overweight individual with low muscle mass.
Because BMI is based solely on height and weight, it does not take into account what factors contribute to those values. This is one of the reasons why body composition scans are so valuable. Hydrostatic weighing is able to accurately isolate fat and fat-free mass in the body to provide an accurate image of your wellness.*
Note: BMI is a valuable measurement for evaluating the stress on joints as a result of weight. Every pound of body weight places four to six pounds of pressure on each knee joint, irregardless of contributing factors.
How do I prepare for Hydrostatic Weighing?
Following the proper test protocols for a hydrostatic weighing test is important to ensure accuracy:
Do no eat during the four hours prior to testing.
Do not ingest gas-producing foods/drinks (e.g. fruits, vegetables, whole grains, beans, or soda) 12 hours prior to testing.
Do not engage in strenuous exercise in the four hours prior to testing.
This test requires a tight-fitting, lightweight swimsuit.
Please bring a towel.
How often should I test?
How often you should test depends on the intensity of your training/nutrition plan. We typically recommend testing every 3, 6, or 9 months, but Hydrostatic Weighing is uniquely suited for more frequent testing.
Frequent Monitoring
Hydrostatic Weighing is safe, affordable, and completely non-invasive, making it especially suitable for frequent, longitudinal tracking of body composition and metabolic changes over time. If you are entering a bulk or cut, or training for a race or competition, you may want to check-in on your body fat and lean mass every month (or more) to ensure you are making progress toward your goals.
Combining Tests for Best Results
A common problem people experience when trying to change their body composition is not fully understanding how diet and exercise affect muscle growth and metabolism. Cutting calories too much or overexercising can sometimes have the opposite effect you’d expect: Metabolism can slow or your body can break down muscles for fuel instead of building them.
Getting frequent Hydrostatic Weighing Tests is a great way to ensure your body composition is changing how you want, but it won’t give you a comprehensive picture of what’s happening inside your body. A Resting Metabolic Rate Test (RMR) is the perfect companion for Hydrostatic Weighing. This test measures how many calories your body burns per day at rest and is critical for designing a personalized and effective nutrition plan.
What results are included with Hydrostatic Weighing?
Total Body Composition
Body composition scans with Hydrostatic Weighing provide precise and accurate data on total body fat percentage, total fat mass, and fat-free mass as well as body density and lung volume.
What is body composition?
Body fat, otherwise referred to as Adipose Tissue, is a connective tissue found throughout the body that regulates metabolism by communicating with both organs and the central nervous system through the release of hormones. The presence of sufficient body fat is an important part of a healthy body and plays several important functions, but becomes dangerous when it builds up in excess.
Adipose Tissue
Adipose tissue increases as a result of fat cells growing in both size and number. Consuming too many calories over a long period of time causes the size of fat cells to grow and be stored across the body. Dieting or other weight loss strategies can shrink the size of these cells, but once created they cannot be destroyed. Larger fat cells are more resistant to insulin, leading to increased risk of Type II diabetes and cardiovascular disease. This is part of the reason why increased levels of fat in the body are associated with heart disease, stroke, Type II diabetes, cancer, and early mortality.
There are three main types of adipose tissue that perform different and very important functions in overall body function:
White Fat
White fat is what one typically thinks of when talking about “body fat.” It is designed for fat storage and found mostly commonly around the belly, hips, and thighs. This is the fat that you can grab in your hand (subcutaneous) or accumulates around your organs (visceral). White fat cells secrete over 50 types of hormones, enzymes, and growth factors which drive food intake, insulin sensitivity, and insulin secretion. An excessive amount of white fat disrupts hormone function, causing a number of health issues such as heart disease, stroke, Type II diabetes, cancer, and early mortality.
Brown Fat
Brown fat’s primary function is to produce heat in cold temperatures, protecting the body from hypothermia. Because this happens by breaking down sugar and fat to create energy, brown fat is also involved in regulating the metabolism of these substrates.
Brown fat is highest in infancy and decreases with age.
Beige Fat
Beige fat cells have a combination of white and brown fat cell characteristics. They are typically found within white cell clusters near the collarbone and spine. These cells are a combination of other fat cell types because although they are believed to be derived from white cells (through a process called “browning” which is a result of exposure to cold temperatures, good nutrition, and exercise), they burn energy like brown fat cells.
What is a “normal” body fat percentage?
The pounds of fat and lean mass which are considered healthy for each unique body depends on a number of variables including height and age. So, in order to evaluate if your fat mass is within normal limits, we use the body fat percentage measurement to make everyone’s unique data comparable.
Fitnescity uses population data to compare your results with Fitnescity customers who are similar to you. After receiving your Fitnescity Dashboard, you will be able to see how your body fat percentage compares to Fitnescity test population averages for those of the same age, gender, and race as you.
FAQs
Why should I test with Fitnescity?
By booking with Fitnescity, you receive easy-to-understand digital insights, a personalized dashboard that allows you to view your progress over time, and a physician follow-up call so you can go over your results in depth.
Find more answers or chat with a team member in our Help Center
* Individual location results may vary
**Individual location process may vary
Fitnescity does not provide medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified medical professional if you have any questions about your results.