How Reliable is Your Body Composition Scan?

by | SportLab

Key Take Aways

Dr. David Looney’s study, run with CoachMePlus, University at Buffalo, and USARIEM, tests how trustworthy a common body composition scanner really is:

  • Testing MF-BIA (bioelectrical impedance) on military-age adults across five morning lab visits over three weeks under tightly controlled conditions, day-to-day results were highly consistent, but compared to DXA (the gold-standard scan), the device underestimated body fat percentage by about 3-4% and read higher fat-free mass.
  • That makes MF-BIA reliable for tracking an individual’s changes over time in consistent conditions, useful for training adaptations, clinical monitoring, and large-scale screening like military body composition programs, but its numbers aren’t interchangeable with DXA results.

Body composition scanners are everywhere now. You see them in gyms, clinics, and military bases because they are fast, painless, and easy to use. One of the most popular options is multifrequency bioelectrical impedance analysis (MF-BIA), which uses safe electrical currents to estimate how much fat, muscle, and bone you have. But how much can you trust the numbers you get? Researchers from CoachMePlus, the University at Buffalo, and the U.S. Army Research Institute of Environmental Medicine (USARIEM) published a study on whether MF-BIA was reliable and accurate when measuring body fat, fat-free mass, and body water.

How was MF-BIA validated in this study?

The research team tested how reliable the results of a commercial MF-BIA system were when measured on healthy, military-age adults twice-a-day on five morning lab visits over a three-week period. Study participants tested at the same time of day under tightly controlled conditions with no exercise, food, caffeine, alcohol, or nicotine beforehand. Measurements were also compared between MF-BIA and dual-energy x-ray absorptiometry (DXA), one of the most precise body composition methods available.

How Reliable and Accurate is MF-BIA?

The researchers found that MF-BIA measurements taken repeatedly each morning were highly consistent. Some day-to-day variation was present, but differences were too small to matter for real-world tracking. When MF-BIA was compared with DXA, body fat percentage was underestimated by about 3-4%. The MF-BIA system also consistently recorded lower fat mass and higher fat-free mass than DXA.

Key Findings from MF-BIA Research

MF-BIA has excellent reliability and minimal day-to-day variability but generally overestimates body fat and muscle mass compared with the gold standard DXA. This means you can confidently track changes in body composition over time in consistent conditions using MF-BIA. Just keep in mind that the results are not interchangeable with DXA. Altogether, MF-BIA is a valuable tool for monitoring training adaptations, following health trends in clinical or fitness settings, and supporting large-scale screening assessments such as military body composition programs.

Reference

Looney, D. P., Schafer, E. A., Chapman, C. L., Pryor, R. R., Potter, A. W., Roberts, B. M., & Friedl, K. E. (2024). Reliability, biological variability, and accuracy of multi-frequency bioelectrical impedance analysis for measuring body composition components. Front Nutr, 11, 1491931. https://doi.org/10.3389/fnut.2024.1491931