DEXA vs. InBody: What's the Difference?

If you’ve had your body composition checked at a gym or wellness studio, it was probably an InBody — you stand on a platform, hold two handles, and get a printout in under a minute. A DEXA scan works differently, and the difference matters when you’re trying to track real change over time.

How each one works. A DEXA scan passes two low-dose X-ray beams through your body. Fat, lean tissue, and bone each absorb those beams differently, and a detector maps what passes through — so DEXA measures the three compartments directly. InBody uses bioelectrical impedance analysis (BIA): it sends a small electrical current through your body and measures the resistance. Because lean tissue holds much more water than fat, the device estimates your total body water and then uses population-based equations to calculate lean mass and fat mass. It’s an indirect estimate rather than a direct measurement.

Precision. This is the practical difference. DEXA’s measurement error for body fat is roughly 1–2%, and under consistent conditions its test-retest precision is tight enough to detect small changes. BIA estimates typically vary by around 3–5%, and because the method depends on body water, results shift with hydration, recent meals, exercise, and time of day. A large 2025 real-world comparison of the InBody 770 against DEXA found BIA underestimated body-fat percentage by several points on average under typical conditions.

What each measures. DEXA breaks results down region by region — arms, legs, trunk, left versus right — and also measures visceral fat and bone density, which InBody cannot assess directly. InBody is faster, cheaper, and widely available, which makes it convenient for frequent check-ins.

Which is right for you. They serve different purposes. If you want a quick directional check between visits, InBody does that well. If you want a precise baseline and the ability to see whether a small change is real — real muscle gained, real fat lost, rather than a hydration swing — DEXA is the more reliable measurement. Many people use both: DEXA a few times a year for the accurate picture, InBody in between for convenience.