DEXA Scan for Body Composition

What is a DEXA scan?

Dual Energy X-Ray Absorptiometry (DEXA / DXA) is widely regarded as one of the most proven and reliable technologies for measuring body composition. DEXA technology provides comprehensive, precise measurements of total body fat percentage, along with segmental body fat distribution in regions such as arms, legs, android (waist) and gynoid (hips).

The DEXA scan can be used to obtain an initial body composition assessment and to understand how the body is changing over time – i.e. how much the lean and fat tissue changes over time, therefore measuring the impact of training or dietary programs.

DEXA's body composition capabilities can also measure the visceral fat content in the android (waist) region. Abdominal, or visceral, fat is of particular concern because it's a key player in a variety of health problems — much more so than subcutaneous fat, the kind you can grasp with your hand. Visceral fat, on the other hand, lies out of reach, deep within the abdominal cavity, where it pads the spaces between our abdominal organs. Last but not least, DEXA provides additional results on bone density.

About DEXA / DXA body composition analysis

Looking beyond the bathroom scale.

Accurate measurement of body composition provides valuable information for assessing, monitoring the human body.

Most people are used to stepping on a scale from now and then. But monitoring weight – while helpful – is not a precise way of assessing health and fitness progress.

Body composition measurement with dual-energy X-ray absorptiometry (DXA) can look beyond weight and the traditional body mass index (BMI) to determine body fat distribution.

What are the benefits?

The DEXA / DXA body composition measurement technology provides far more complete and precise information than any other weight and and body fat assessments tool.

Body composition measurement with dual-energy X-ray absorptiometry (DEXA / DXA) helps individuals, trainers and physicians monitor the effects of diet and exercise in a precise manner.

Precise, accurate and segmental (regional) body fat data can have many benefits such as:

• Supporting decisions on training regimens and nutrition plans.

• Understanding and monitoring health risks related to body fat distribution and bone density.

Moreover, the measurements are fast and non invasive.

What type of results does a DEXA scan provide?

DEXA results often include bone density as well (bone mineral density - BMD).

Please note that DEXA scans do subject you to small amounts of radiation.  A whole body scan produces a level of radiation equivalent to flying by airplane from New York to California.

What is a good DEXA body fat percentage?

Total body fat percentage percentile chart

The chart is based on the National Health and Nutrition Examination Survey (NHANES), which collected large-scale data on whole body DXA scans of participants age 8 years and older to provide nationally representative data on body composition. The study also collected data to study the association between body composition and other health conditions and risk factors, such as cardiovascular disease, diabetes, hypertension, and activity and dietary patterns.

Fitnescity's  "Total Body Fat Percentage Percentile Chart" presents body composition data from whole body DXA scans for individuals who participated in the 1999–2004 NHANES. Measures for the total body and regions of the body also include total mass, fat mass, percentage fat, lean soft tissue (excluding bone mineral content), and fat-free mass (including bone mineral content).

How to use the chart

1- Select your gender and ethnicity/race using the dropdown bar at the top of the chart. Identify your age group and your body fat percentage on the chart. 

2- Identify the point where your x and y axis intersect. Depending on what color it falls under, you will be in one of the percentiles (5th, 10th, 15th, 25th, 50th, 75th, 85th, 90th and 95th).

3- Your percentile will indicate the percentage of people who are similar to you and who have a lower body fat percentage.

Example:

For instance, if you are in the 25th percentile, this means that 25% of individuals who have the same gender, ethnicity and age as you have a lower body fat percentage. The lowest percentiles are typically found in elite athletes, while the highest ones are associated with very high body fat risk.

Visceral Fat: The Invisible Health Risk

It is well-established that both the distribution and volume of fat, especially visceral adipose tissue (VAT), is a predictor of future health. While normal amounts of visceral fat pad and protect organs, an excess amount of VAT is strongly associated with metabolic syndrome and increases health risks for cancer, stroke, diabetes, cardiovascular disease, and hypertension.1, 2, 3 Excess VAT can impact lifestyle by increasing the risk of dementia, depression, arthritis, sexual dysfunction, and sleep disorders. Storing excess fat around the organs increases the production of inflammatory substances that interfere with hormones that control appetite, weight, mood, and brain function.

There are several methods for quantifying VAT, including waist-to-hip measurement, bioelectrical impedance, dual-energy absorptiometry (DEXA), CT, MRI, and ultrasound. Although CT is considered the gold standard because of its accuracy and reliability, its drawbacks are exposure to ionizing radiation and the relatively high cost of a CT exam. DEXA has been found to be an accurate means for measuring VAT volume and is generally more accessible to the general population.

DEXA offers several advantages compared to CT including reduced radiation dose, decreased scan times, and lower cost.4 Importantly, obtaining VAT measurements with DEXA is easily performed in conjunction with evaluation of bone mineral density, fracture assessment and risk, and whole body composition.5

Learn more: Visceral Fat: The Invisible Health Risk - Vyvyane Loh, MD CEO and Medical Director Transform Institute for Metabolic & Lifestyle Medicine.

Fitnescity has the largest network of DEXA scan partners in the US.

How it Works

Bone density

Bone density refers to the amount of minerals (mostly phosphorus and calcium) in your bones. The more mineral content, the “denser” (and stronger) your bones. Bone density testing measures the strength of your bones. It can also reveal whether you have a bone disease and predict how likely your bones are to break.

For instance, osteopenia is a loss of bone mass that causes your bones to become weaker which stems from the loss of calcium. When you start losing calcium, your bones can become more brittle. Your body is unable to replace the calcium as fast as it loses it and eventually, this can lead to another serious bone condition called osteoporosis.

Osteoporosis also weakens the bone, but it’s more serious than osteopenia. Your bones become so thin that even a slight bump against the wall can lead to a fracture or break. Your bones may even start to form holes, or pores, because so much material has been lost.

Anyone can develop osteopenia or osteoporosis. But these bone diseases tend to affect individuals over the age of 50 more than younger people. And women are usually impacted more than men.

Studies show that 50% of women and 20% of men will break a bone at some point in their lives due to osteoporosis. It’s considered a silent disease because a broken bone is usually its first clear sign. It’s not something you can feel happening inside your body, and you certainly can’t see it.

About the DEXA machine

The most commonly available DEXA scan machines are GE’s Lunar iDXA and Hologic’s Horizon DXA system. Both provide results with clinical-grade accuracy. Here’s an overview of each machine.

Lunar iDXA by GE

Clarity

Crisp, high resolution images and precise measurements to help capture body measurements with confidence. Assessment is made easy with Lunar iDXA system's extra-crisp images. Lunar iDXA offers the latest generation of DXA technology from GE Healthcare. Its vertebral assessment is comparable to radiographs in identifying and classifying deformities concerning etiology, grade, and shape, while using a lower dose of radiation.

Precision

Lunar iDXA's detector technology enables an extremely precise measurement of the bone, allowing to track changes that had previously been too minor to detect.

Versatility

Lunar iDXA is equipped with a wide range of clinical applications with the enCORE software platform that helps professionals leverage the best of the DXA technology —whether it is for research projects in bone health and body composition, i.e. fat and lean mass distribution and trending for metabolic health applications, or for commercial use.

Horizon DXA system by Hologic

The Advanced Body Composition® Assessment, available with the BodyLogic™ scan on the Horizon® DXA system, visually presents data from BodyLogic scan in a series of easy-to-read graphical reports. Results are available immediately and use color mapping to identify fat, lean muscle mass, and bone.

The reports provide detailed information on Body Fat %, Lean Muscle %, and Visceral Fat with a comparison against the National Health and Nutrition Examination Survey (NHANES) database of age, gender and race matched peers.

Additionally, regularly scheduled BodyLogic scans during the course of a weight management program will show if the weight loss is from fat stores – or from muscle. The Rate-of-Change report, a key report available with the Advanced Body Composition® Assessment, visually displays changes in the body over time, enabling users and professionals to assess and adjust treatment programs.

Overall, the Advanced Body Composition® Assessment serves as an additional tool to monitor an individual’s weight loss and weight management program. When used in conjunction with weight management programs, data from the Advanced Body Composition® Assessment can be used to help individuals lose body fat, not muscle mass, for a more successful and healthier long-term weight loss.

1. Visceral fat: What It is and Why It’s So Dangerous. Dr. Axe website. http://draxe.com/visceral-fat/ Accessed March 1, 2016.

2. The Viciousness of Visceral Fat. Health and Fitness Talk website. http://www.healthandfitnesstalk.com/the-viciousness-of-visceral-fat/ Accessed March 1, 2016.

3. Visceral fat tied to coronary disease. AuntMinnieEurope website. http://www.auntminnieeurope.com/index.aspx?sec=prtf&sub=def&pag=dis&itemId=612953&printpage=true&fsec=sup&fsub=car Accessed May 5, 2016.

4. Kaul S, Rothney MP, Peters DM, et al. Dual-energy X-ray absorptiometry for quantification of visceral fat. Obesity (Silver Spring). 2012;20(6):1313- 1318.

5. Choi YJ. Dual-Energy X-Ray Absorptiometry: Beyond Bone Mineral Density Determination. Endocrinol Metab (Seoul). 2016;31(1):25-30.

Additional Resources from Hologic

• Changing Body Composition: Using metabolic testing and DXA to improve fitness and health

  Joseph B. Norris, MD, McLean County Orthopedics, Bloomington, IL

• Expanding Role of DXA in Patient Health and Human Performance

  John Shepherd, PhD, CCD, Professor of Radiology & Biomedical Imaging at UCSF School of Medicine

• The Scale Lies: Why the DEXA Scan Is Best

  Keith Norris, contributing coach at breakingmuscle.com

• DXA beats BMI: Using an X-ray Exam to Measure Body Composition & Fat Loss

  UCSF Department of Radiology and Biomedical Imaging

• DXA Body Composition for Better Health

  Marilyn McKenna, weight loss blogger

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.