From smart scales at home to BEI body composition scales at the gym, there’s an increased awareness of the importance of body composition for our health and fitness.
This is good news – when compared to limited calculations such as BMI, body composition measurements give us a more nuanced look at a person’s health and fitness. Plus, research has shown that healthy body composition can increase lifespan, in part by reducing the risk of heart disease, cancer, high blood pressure, Type 2 diabetes, and insulin resistance.
But what is a “healthy” body composition, and what does it look like for you?
A body composition scan is the most accurate method of assessing your body composition and can be used alongside other health and fitness tests to access a wealth of data about well-being.
What is a body composition scan?
A body composition scan, or DEXA scan, is an imaging test that gives an in-depth analysis of your body composition, including fat, muscle, and bone density.
The DEXA is the gold standard for body composition testing, making use of the same medical-grade technology as you would find in a hospital bone density scan.
How does a DEXA scan work for body composition?
DEXA stands for dual-energy x-ray absorptiometry. While the name might sound complicated, the scan is simple: two low-level X-ray beams are passed over the length of the body. The test takes around 8-9 minutes for both body composition and bone density testing and is safe, precise, and reliable.
Since different body tissues such as muscle, fat, and bone absorb X-rays at different rates, the DEXA scan can build a precise body composition map by examining the rates of absorption in different areas of the body.
Are body composition scans accurate?
In short, yes. A DEXA scan is a precise and reliable measure of body composition.
With a standard error of just 1-2%, DEXA is more accurate than other measures such as skinfold measures and bioelectrical impedance analysis (BIA), both of which can have errors of up to 5%.
To view a full comparison of body composition tests including bioelectrical impedance analysis and skinfold measures, check out our ultimate guide to health and fitness testing.
What does a full body composition scan show?
A DEXA scan report gives an extremely detailed breakdown of body composition.
Let’s take a look at the four main metrics that a DEXA body composition scan shows: fat mass, lean mass, bone mineral content, and the android: gynoid ratio.
One of the metrics that many individuals seeking a body composition scan are most interested in is their body fat percentage.
Unlike other body composition technologies, what’s great about a DEXA scan is the level of insight we can offer into body fat, including its type, location, and how it tends to be stored in your body.
A DEXA scan can offer a detailed analysis of the following:
- Body fat mass: Total mass of fat on your body, including both subcutaneous and visceral fat (measured in grams)
- Body fat percentage: Body fat mass as a percentage of total mass
- Visceral adipose tissue (VAT): The amount of visceral fat in your body (measured in grams, cm², or cm³)
- Android to gynoid ratio: A descriptor of where fat tends to be stored in your body (described as a ratio)
Visceral fat – also known as “hidden fat” – is fat that’s stored in the abdominal cavity and wraps around our body’s organs, such as the liver and intestines. Unlike subcutaneous fat, which is located under the skin and can be measured using skinfold measures, visceral fat isn’t visible/able to be grabbed.
This is why understanding not only how much fat is stored in the body, but where it is stored, is so important to assessing our health.
The second element of body composition that a DEXA can accurately measure is lean mass.
Lean mass includes the total amount of muscle mass, as well as tissues such as organs. When lean mass is added to BMC (bone mineral content), we can gain a measurement of the total amount of fat-free mass in the body.
- Lean mass: Total quantity of muscle mass + other tissues
- Fat-free mass: Lean mass + BMC (bone mineral content)
- Lean mass index: Lean mass/height²
As well as measuring these metrics for the body as a whole, a DEXA scan also takes measurements for 6 specific body areas: the left arm, right arm, trunk, left leg, right leg, and head. This can be particularly useful for highlighting any muscular imbalances in the body, which would be indicated by more than a 10% lean mass difference on the left and right sides of the body.
Bone mineral density
Within medical contexts, a DEXA scan is often used to calculate bone mineral content to assess for osteoporosis risk. A body composition scan can be performed with or without this essential test for bone health, depending on your specific goals.
Bone mineral density is a measure of how much calcium your bones have relative to their overall size. This is calculated as:
Bone Mineral Density (BMD) = Weight of bones (g) / Size of bones (cm²)
The DEXA scan can give you the following metrics:
- Bone mineral content (BMC): Total bone weight (in grams)
- Bone mineral density (BMD): BMC/size of bones (in g/cm²)
- Z-score: Bone density compared to your age, sex, and ethnicity
- T-score: For those over the age of 40, bone density compared to a healthy 30-year-old
This information can help to identify a risk of osteopenia or osteoporosis, indicating that seeking a formal diagnosis might benefit you. It can also help highlight certain lifestyle changes that might be beneficial, such as increasing nutritional sources of calcium, magnesium, and vitamins K2, D3, and C in the diet, and tailoring your exercise regime to improve bone health.
As mentioned earlier, the android-to-gynoid ratio (A/G ratio) is a descriptive measurement of where body fat is stored.
- Android: Fat stored in the abdomen and midsection, as in an “apple” body shape, which is more common in men and those with higher levels of testosterone.
- Gynoid: Fat stored in the hips, thighs, and bottom, as in a “pear” body shape, which is more common in women and those with higher levels of oestrogen.
The android/gynoid ratio is simply the android fat divided by the gynoid fat. This number (which typically falls within an approximate range of 0.5-1.5) is used to describe the way your body tends to store fat.
While this ratio isn’t something that we’re able to change in any significant way without altering our hormonal makeup, it can serve as a useful means of understanding how (and where) we will lose or gain fat first.
Understand your body composition with a DEXA scan at My Vital Metrics
A DEXA scan is the most accurate type of body composition analysis, offering actionable insights based on your fat mass, lean mass, bone health, and more.
To book a body composition scan or schedule your free fitness and nutritional consultation, reach out to My Vital Metrics today!