Acute water ingestion influences lean soft tissue estimation from dual-energy x-ray absorptiometry: implications for clinical diagnosis.

BACKGROUND & AIMS: Dual-energy X-ray absorptiometry (DXA) is a common method for estimating lean soft tissue (LST), which is crucial for diagnosing skeletal muscle conditions (e.g., sarcopenia). However, the accuracy of DXA can be compromised by external factors, including acute water ingestion (AWI). While prior research indicates AWI can inflate LST measurements, the dose-response relationship and the specific impact on regional body composition such as trunk vs. appendicular LST (ALST) remain unclear. The primary purpose of this study was to determine the dose- and time-dependent effects of AWI on the estimation of DXA-derived whole-body LST, trunk LST, and ALST. METHODS: In a randomized controlled trial, 46 participants (n = 26 males, n = 20 females) were assigned to control (no water, n = 11), 250 mL (n = 12), 500 mL (n = 11), or 1000 mL (n = 12) of AWI. Body composition was measured using DXA at baseline and then immediately after (IP), 30 (P30), 60 (P60), and 90 (P90) minutes after water consumption. RESULTS: Higher volumes of AWI led to significant increases in whole-body LST. Regardless of timepoint, 1000 mL AWI significantly increased LST compared to all other groups. Significantly higher LST was observed in the 500 mL group at P90 compared to 250 mL and control. Notably, this increase was primarily localized to the trunk region, which accounted for 53% to 99% of the change in whole-body LST. Conversely, AWI had no significant effect on ALST. CONCLUSIONS: AWI is a significant confounding factor that may inflate DXA-derived estimates of whole-body LST. However, as the effect is localized to the trunk, it may be less likely to impact ALST-based sarcopenia classification. To ensure the accuracy of whole-body assessments, standardized protocols should recommend limiting water intake to <500 mL within 90 minutes of a DXA scan.