Here are the deets on the DEXA body scan and why it’s one of the most powerful wellness tools available.
So, you started hitting the gym five days a week. You’ve been working with a trainer to get the right mix of movements in your workout. You’re also being proactive in eating more fruits and veggies and healthy fats, which surely would make a difference in your health. And yet, your clothes still fit about the same. Your body mass index (BMI) hasn’t changed much. And that scale is not budging.
That’s because weight and BMI alone are not the only indicators of progress.
BMI has long served as the standard for determining healthy weight ranges. That’s why many people use it to track their progress. But BMI alone isn’t the end-all metric that decides your level of health.
That’s because BMI provides limited information about your weight and height ratio. It doesn't delve into body composition details—and it’s these details that reveal your risk of chronic illness and show how much progress you’re making from diet and exercise.
For example, muscle weighs about the same as fat, but it is much denser and more compact. Increasing muscle mass also increases your metabolism. So even if your scale seems stuck, you could still be getting healthier by putting on more muscle. By the same token, losing weight isn't necessarily healthy if you're losing muscle rather than fat.
So how do you know if you’re going in the right direction? A DEXA scan will tell you the exact percentage of your lean muscle, bone mass, and different types of fat. When you get multiple DEXA scans over time, you can compare your results and see how much progress you’re really making. Explore these five facts about DEXA to understand why this scan can revolutionize your diet and exercise regimens.
Tackling the Technology: How Does DEXA Work?
A DEXA scan takes two low-radiation X-rays of your body. By looking at how different areas absorb these rays, we can differentiate between bones and soft tissue and the various types of fat and muscle. This scan provides a safe look at your entire body composition using about 10% of the radiation exposure you would receive from a normal chest X-ray. Doctors consider DEXA the most reliable way of measuring body fat.
Fun fact: DEXA stands for dual-energy X-ray absorptiometry, which makes sense when you consider that the technology uses two (dual) X-rays.
The Background of Bone Density
While a bone density scan usually focuses solely on the spine and hips, a DEXA scan for healthy body composition covers your entire frame to get a true picture of your internal makeup. A localized version of the DEXA test is the standard for diagnosing osteoporosis, a loss of bone density that results in fractures.
By the way, most women should start getting bone density tests at age 65, but your doctor may recommend you start at age 60 if you are White or Asian, have a small frame, or have a family history of osteoporosis.
If you get a DEXA screening for bone density, your results will include a Z score. The Z score compares your bone density to that of a younger person of the same sex and provides information about osteoporosis risk as follows:
Normal bone density: -1.0 or higher
Low bone density (osteopenia): -1.0 to -2.5
Osteoporosis: -2.5 or lower
Beyond BMI: Info You Can Glean from a DEXA Scan
So, let’s say you decided to go for it and went to get your first DEXA scan. Good for you! But when you’re handed the results, you’re suddenly transported back to your high school foreign language class―nothing makes sense!
Your DEXA scan report does speak a “language” all its own, but it’s not impossible to understand . Let’s take a crash course on the lingo you’ll see on your report so that you can compare values over time with every scan you receive:
Android to gynoid ratio describes the placement of fat mass within the body. People with a so-called "pear" shape store fat around the hips (gynoid), while an apple shape or android shape collects fat around the abdomen and stomach. A healthy android to gynoid ratio is about 1.0 for men and 0.8 for women. Fitnescity also provides regional body fat results with information about the fat in the torso, pelvic area, and extremities.
Total body fat percentage, written as %BF. Tracking this number over time shows you the impact of your nutrition and exercise regimen. %BF in DEXA is unique to DEXA and can’t be compared across other methods of body fat measurement. An even better indicator of change is monitoring your percentile as compared to other people of similar age, gender and race to you.
Visceral adipose tissue (VAT) is a type of body fat that accumulates around the internal organs rather than under the skin, which is your subcutaneous fat. These fat cells grow larger if you consume more calories than you burn off through metabolism and exercise. VAT is associated with dangerous hormone activity that increases the risk of diseases related to metabolism, such as diabetes and heart disease. Too much visceral fat also raises the risk for gallbladder disease and breast cancer in women and may lead to worse outcomes for individuals who have cancer. Understanding your body's visceral fat content can help you map a plan to reduce disease risk.
Resting metabolic rate (RMR) estimates your body's calorie needs at rest. The higher your RMR, the better you burn calories while exercising—this is known as metabolism. You can boost your RMR by increasing your muscle mass and reducing your body fat percentage, with regular DEXA tests to keep you on the right track. Although the DEXA provides a ballpark reading of your RMR, you can get a more accurate measurement from metabolism RMR testing.
Skeletal muscle mass (SMM) measures your bone mass. While SMM is only an estimate, DEXA provides the same level of accuracy for this metric as an MRI or CT scan. %SMM refers to the percentage of bone mass compared to total mass.
Fat-free mass index (FFMI) compares the combined mass of your connective tissue, organs, bone, and muscle to your height. You can track your FFMI to see your progress in building muscle mass.
Fat mass index (or FMI) is defined as the ratio of fat mass in kilograms to height in meters. FMI is different from BMI, which compares your weight to your height and does not account for differences between fat and lean mass.
Intracellular and extracellular water measures the water both inside and outside your cells. More than half of an adult’s body consists of water, including the fluid within the blood, muscles, fat, and other body tissues. Only some DEXA scans provide a segmented breakdown of this information.
Fun fact: You should drink about two to three liters of fluid every day to remain hydrated. Just accept that a lot of bathroom breaks are in your future—there’s no way around it. The exact amount of water intake varies based on gender, weight, and daily level of physical activity.
The Power of Precise Data
When you get a second or third DEXA scan, you have the benefit of comparing your results over time. But what if this is your first scan? That’s where the power of data comes in handy.
DEXA compares your results with national data so you can see exactly where you stand. Simply click on a data point to see the average numbers for others based on ethnicity, sex, and age. The database draws from the National Health and Nutrition Examination Survey, which includes DEXA scan results from a collection of thousands of participants ages 8 and older from 1999 to 2004.
Fun fact: The NHANES initiative from the Centers for Disease Control and Prevention also gathers data on everything from blood pressure and growth to income and consumer behavior to understand how our lives impact our health and wellness.
Looking at these numbers and understanding what they mean can guide your diet and exercise choices. For example, if you have low muscle mass and high body fat compared to others of your age and sex, you may want to focus on reducing fat and building lean mass. Fitnescity’s digital dashboard makes it easy to share your scan results with your trainer, coach, or nutritionist so they can help you move in the right direction. Getting three or four scans each year can show you whether your efforts are paying off, helping you stay on track with your goals.
What to Expect During the Scan
Getting a DEXA scan is a lot like using a scanner to import a document to your computer—except the scanner looks more like a bed, and your body is the paper. It doesn’t hurt or even tickle, and you’ll be in and out in about 30 minutes when you visit a Fitnescity location.
When you schedule a DEXA scan near you, carefully review the instructions to prepare for your appointment. If you take calcium supplements, you may need to discontinue their use 24 hours before the test. However, you can exercise, eat, and drink as you normally would on the day of your scan.
During the 10-minute scan, you’ll need to stay relatively still. Wear form-fitting, comfortable clothes and avoid clothing or accessories that have metals or hard plastics, such as hairpins, underwire bras, watches, jewelry, buttons, and zippers. Let the test provider know if you have a pin in your bone or a joint replacement before the scan.
Scheduling a DEXA scan every three to six months as a way to check in with your fitness level can be powerful motivation when you see your numbers improving.
At Fitnescity, we use medical-grade, FDA-approved equipment to complete your DEXA test, treated as the gold standard for healthy body composition accuracy among health care providers. When you're ready for a DEXA scan near you, schedule an appointment in your state and discover the numbers that really matter for your health.
References
Bone Density Scan (DXA or DEXA) | UCSF Radiology
DEXA Scan to Measure Bone Density
Osteoporosis - Symptoms and causes
DEXA scan: Purpose, procedure, and results
DXA Body Composition Information
NHANES - National Health and Nutrition Examination Survey Homepage