New InBody Test

I'm excited to announce that Fit now has the InBody body composition test. The InBody is Bioelectric Impedance type of body composition measurement and it is the final type outlined below. You may recall that we had previously been measuring body fat using the Fit3D scan. Please reach out to me to schedule your InBody body composition test. I absolutely consider the InBody more accurate than the Fit3D scan. There several different ways to measure body composition, with some being more accurate, reliable, or replicable than others. I've outlined them below:

Skinfold Calipers
This is also known as pinch test. As the name implies, this method involves pinching the subcutaneous fat layer with fingers and measuring the thickness using a caliper.
Calipers are easily portable, and measurement is simple and inexpensive. However, this method involves estimating the total Percent Body Fat (PBF) based on subcutaneous fat.
Although a large portion of body fat is subcutaneous fat, the measurement may not be accurate for people whose body fat distributions vary. Also, measurement is difficult if the subcutaneous fat layer thickness is 5 cm or more and reproducibility of the result varies greatly depending on the skills of the measurer.

Hydrostatic Weighing
Underwater weighing calculates the total body fat by the density of the body. It is based on Archimedes’ principle: when an object is submerged in water, the difference between the mass of the object in the air and its mass in water is the object’s volume.
Body density = Mass of air /(Mass of air – Mass of water )
Underwater weighing is regarded as the gold standard for body composition measurement as it is one of the only body composition technologies that have been compared directly to cadaver analysis. Unfortunately it is very uncomfortable as the examinee has to exhale all the air from the lungs prior to fully submerging in water.

Air Displacement Plethysmography
This method measures the volume of a human body by measuring the volume of air according to the changes in pressure in a chamber.
First, weight and volume of the person are used to calculate body density and then Percent Body Fat and the fat-free ratio.
Density = Mass / Volume
Percent Body Fat = (495 / Density) – 450
Fat free ratio = 100 – BF%
Time required for measurement is relatively short at 3-5 minutes and the examinee can continue breathing in the chamber as opposed to underwater weighing. This method is known as a gold standard because it allows body composition analysis and produces accurate measurements using volume just like underwater weighing. This is often called the "Bod Pod" due to its appearance.


Dual Energy X-Ray Absorptiometry (DEXA)
DEXA is an imaging method that measures the body weight in terms of BMC, lean, and fat based on the decrement of X-ray on the images obtained by exposing to two different X-rays. With the patient lying down, photons of the X-ray beams of different energy levels scan the patient. It takes about 5 to 30 minutes.
As a standard method for body composition analysis, DEXA has high accuracy along with hydrodensitometry. Its advantage is that it can measure the body composition of bone density, body fat and muscle mass for different parts. Advancements to the technology affords DEXA the ability to differentiate lean and fat, allowing this technology to advance from a 2 compartment model to a 3 compartment model.
In order to get a DEXA scan performed, you will typically need to make an appointment with a hospital or clinic that has a DEXA device. You may need to do some research; not all hospitals and clinics will have DEXA devices. You can get a free DEXA scan at the UCSD Bone School (more info).


MRI (Magnetic Resonance Imaging)
Magnetic resonance is a form of imaging technique where the body water may be mapped (but not quantified). The body is scanned in segmental (slices) scans are used to predict whole-body values. MRI is considered to be the most accurate tool for in vivo quantification of body composition. It is an ideal evaluation tool for measurement of skeletal muscle mass and adipose tissue (and can divide adipose into visceral and subcutaneous depots).
MRI’s use a high-strength magnet, thus all metal must be removed. Individuals with metallic chips, materials, surgical clips, artificial joints/prosthetics, pacemakers, metal implants, artificial heart valves, metallic cochlear implants, bullet fragments, or insulin pumps should not test. However, since there is no ionizing radiation, this is a preferable option for many (elderly, children, etc.)
A whole-body scan is roughly 25-30min for scan and 3 hours to analyze via computer software.

Bioelectric Impedance Analysis (BIA)
Bioelectrical Impedance Analysis (BIA) is a method of measuring impedance by applying alternating electrical currents to a user to measuring their volume of water through impedance values.
This non-invasive method involves the placement of electrodes on a person’s feet, hands, or both. A low-level electrical current is sent through the body, and the flow of the current is affected by the amount of water in the body. BIA devices measure how this signal is impeded through different types of tissue (muscle has high conductivity but fat slow the signal down).
As BIA determines the resistance to flow of the current as it passes through the body, it provides estimates of body water from which body fat is calculated using selected equations. The InBody test only requires the examinee to remove shoes and socks.