The Surprising Role Fat Plays in Muscle and Bone Health
April 9, 2026 Fat, Muscle, and Bone Are a Unified System Bones are not solid — they contain living marrow and fat plays a complex
Summary:
When it comes to body composition testing, we hear from a number of people who ask why they should get a DEXA scan instead of an InBody scan. In short, it’s because DEXA scans are far more accurate. But let’s take a closer look at the DEXA scan vs Inbody question.
An InBody machine uses bioelectrical impedance analysis (BIA) to measure body composition. But what is BIA exactly and how does it work? Basically, an InBody machine sends a small current of electricity through your body. To use it, you stand on the machine and hold the hand electrodes, allowing an electrical current to pass through your body.
The electrical current flows freely through your body fluids but meets resistance when it encounters fat or bone tissue. Using data from the current, the InBody scanner calculates your body composition, considering variables such as age, gender, and height. Accuracy can be significantly influenced by factors such as hydration levels, recent food intake, exercise, and menstrual cycle, however.
For instance, being overhydrated or dehydrated will skew the results, as BIA technology works by measuring water distribution. Eating a large meal before the scan can also affect accuracy. And, when exercising, the body tends to redistribute water in the muscles, once again affecting accuracy.
A recent study found that InBody scan accuracy is also impacted by age and sex. The study tested the validity and reliability of body composition analyzers in children and adults and found that InBody scans tend to underestimate body fat in adults by as much as 4.8%, yet overestimate body fat in children by up to 2.3%. Results were also less consistent in children than adults, and scans were more accurate for girls than boys.
In addition, the study showed that men and women show different levels of body fat estimation when using InBody devices, especially in older age groups. This suggests that sex-specific differences in body composition, such as fat distribution, can impact accuracy.
In short, bioelectrical impedance based measurements tend to be inconsistent and prone to error. DEXA scans, on the other hand, are widely considered to be more accurate than InBody scans for measuring body composition and are able to provide more precise measurements of fat, muscle, and bone.
A DEXA (dual-energy X-ray absorptiometry) scan, also known as a bone density scan, is a low-dose X-ray that measures bone mineral density (BMD) and body composition. According to the World Health Organization, DEXA scans are considered the “gold standard” for measuring BMD and are recognized as the most accurate, reliable, and authoritative measure for measuring body fat and lean muscle mass.
During the test, you’ll be asked to lie on a padded table while a scanner passes over your body. The DEXA scan involves two X-ray beams, each with different energy levels. These beams pass through the bones, and the amount of X-rays absorbed by the bones is measured. Dense bones allow fewer X-rays to pass through, making it possible to calculate bone density. The entire procedure is quick, generally taking around 10-15 minutes to complete, and is painless.
The DEXA scan process involves minimal radiation and is non-invasive, making it a safe choice for most people. The scanner emits a very low level of radiation—much less than a standard x-ray—so it’s safe and non-invasive.
The amount of radiation exposure during a DEXA scan is comparable to the natural background radiation exposure one would experience over a day or two. This makes it a preferable choice for individuals who need frequent scans, such as those monitoring changes in bone density over time.
Once the scan is complete, the data collected is analyzed to calculate body fat (including visceral fat), lean muscle mass and bone density. Results are typically emailed to the user immediately after the scan.
DEXA scans are considered the gold standard for measuring bone density and body composition. They are considered to be far more accurate than InBody scans and are able to provide precise measurements of fat, muscle, and bone, whereas InBody scans can be affected by various factors.
According to a recent study of healthy men and women comparing InBody body composition analyzers to a DEXA scan, InBody analyzers produced systematic bias (i.e., “an error that consistently pushes measurements or findings away from the true value”) when measuring body fat percentage, fat mass, and fat-free mass. The study also found that InBody analyzers produced proportional bias when measuring fat mass in women and fat free mass in men.
While no composition test is 100% accurate, DEXA scans have a very low error rate of 1–2% and are generally considered more accurate and reliable than InBody devices.
April 9, 2026 Fat, Muscle, and Bone Are a Unified System Bones are not solid — they contain living marrow and fat plays a complex
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