For decades, stepping on a scale meant seeing just one number: your weight. But two people weighing 175 lbs can have radically different health profiles depending on their muscle mass or body fat percentage.
Recently, a global commission of experts in The Lancet confirmed that BMI (Body Mass Index) is insufficient as a standalone health measure. To truly understand your health, you need to go further. You need to analyze body composition.
Until now, absolute precision was reserved for hospitals using DEXA scans. But a new 2025 internal clinical study proves that the Withings Body Scan has reached this level of excellence, right from the comfort of your home.
DEXA: The medical gold standard
To appreciate the technological breakthrough of Body Scan, we first need to understand DEXA (Dual-Energy X-ray Absorptiometry). DEXA is widely recognized as the clinical method of reference—the Gold Standard. It is a massive medical imaging device that uses low-intensity X-rays to scan the entire body. It distinguishes lean mass, fat mass, and bone mass with extreme precision.
But getting a DEXA scan is a hassle: it is expensive, time-consuming, and impractical for daily monitoring of your health.
The 2025 clinical study: 99% correlation for Body Scan*
This is where Withings changes the game. A comparative internal clinical study, conducted in collaboration with the sports-health center Mon Stade, tested Body Scan against DEXA with a cohort of 80 participants.
The protocol was rigorous: each participant underwent a DEXA scan followed immediately by three Body Scan measurements to compare results under identical physiological conditions.
The results are undeniable: Body Scan achieved an exceptional correlation of r=0.99 compared to DEXA for total fat mass. But what does correlation mean, and why is it important to understand the difference with precision or accuracy?
A single DEXA scan gives you a snapshot: accurate, but frozen in time. What actually drives health outcomes is the trend: is your fat mass going down, is your muscle mass going up, week after week. And trend-tracking is precisely what a 99% correlation measures: it confirms that when your body composition changes, Body Scan detects that change as reliably as DEXA would.
This is the real advantage of correlation over a single point-in-time accuracy claim. DEXA can tell you where you stand today. Body Scan tells you where you're heading, and does so with a relationship to DEXA data strong enough (r=0.99 for fat mass, 0.98 for muscle mass) that clinicians consider it a validated proxy for tracking purposes.
That's also why daily use matters more than lab-grade precision on any single reading. No one gets a DEXA scan every morning: it's expensive, it involves radiation, and it lives in a hospital. Body Scan's value isn't in replacing that one clinical snapshot; it's in giving you hundreds of consistent data points DEXA never could, so you catch a plateau, a muscle loss trend, or a fat mass shift in real time, not once a year at a checkup.
In short: DEXA is the reference for where you are. Body Scan, validated against DEXA at 99% correlation, is the reference for where you're going.
Here is the breakdown of the correlations found:
Total Fat Mass: 99% correlation.
Total Muscle Mass: 98% correlation.
Total Water Mass: 95% correlation.
Correlation Body Scan vs DEXA - total fat mass plot chart
How is such precision possible?
Unlike standard scales that only have 4 electrodes under your feet, Body Scan is equipped with a retractable handle, bringing the total to 8 electrodes.
This unlocks two major technological advancements:
Segmental body composition: The scale doesn't just estimate your lower half. It sends a safe electrical signal through your entire body, allowing it to measure the right arm, left arm, torso, and each leg independently. This helps detect muscle imbalances or localized fat.
Multi-frequency technology: Body Scan uses very high frequencies (up to 250 kHz) to penetrate deep into cells. This allows it to distinguish between intracellular and extracellular water for ultra-precise analysis, whereas traditional scales often have to "guess" or extrapolate these values.
Why this is a revolution for your health
Democratizing this technology means medical-grade monitoring is no longer an annual event, but a daily habit.
With over 750 million body composition metrics collected over 15 years, Withings proves it is possible to combine the simplicity of a connected scale with the high standards of modern medicine.
*A 99% correlation does not mean that a single body fat measurement taken with Body Scan will be within ±1% of a DEXA measurement, nor does it mean that two consecutive measurements will be within ±1% of each other.