PP188 - CHANGES IN OUTCOME OF BODY COMPOSITION MEASURED WITH BIOELECTRICAL IMPEDANCE AFTER HIGH WATER CONSUMPTION

PP188

CHANGES IN OUTCOME OF BODY COMPOSITION MEASURED WITH BIOELECTRICAL IMPEDANCE AFTER HIGH WATER CONSUMPTION

G. E. C. Slager^1,2,*, D. Iprenburg², N. L. R. Gielen², M. K. Nieuwenhuis^3,4, M. J. Sealy^1,5

¹Research Group Healthy Ageing, Allied Health Care and Nursing, ²Physiotherapie, Hanze University of Applied Sciences, ³Alliance of Dutch Burn Care, Burn Center, Martini Hospital Groningen, ⁴University Medical Center Groningen, Department of Human Movement Sciences, University of Groningen, Groningen, ⁵Department of Gastroenterology and Hepatology, Dietetics, Radboud University Medical Center, Nijmegen, Netherlands

Rationale: According to guidelines, bioelectrical impedance analysis (BIA) should be performed under standardized conditions with minimal recent fluid intake, which may be burdensome for patients. Therefore, this study investigates differences in BIA outcomes up to 1 hour following intake of 1 liter (L) of water without urination.

Methods: 50 KHz BIA was performed using the Bodystat 500. Over a period of one hour, BIA were conducted at five time points: T₀, T₁₅, T₃₀, T₄₅ and T₆₀ minutes. Immediately prior to T₁₅ and T₃₀, participants consumed 0.5 L of water twice, after which actual body weight (BW) was reassessed (BW₁₅, BW₃₀). All measurements were performed in triplicate;  their median was used. Fat-free mass (FFM) and fat mass (FM) were calculated using Kyle formula with FM = BW-FFM. Changes (Δ) in the median (IQR) of FFM and FM were tested with Wilcoxon signed-rank test (p <0.05*) both based on actual BW (BW₁₅ or BW₃₀) and on baseline BW at T₀ (BW₀). 

Results: 80 healthy Caucasian participants (38% male, 63% female) were included: median age: 22 years (21–24), mean BMI 22.6 ± 2.3 kg/m². Median ΔBW₀–BW₁₅: 0.5 kg (0.4; 0.6)* and ΔBW₀–BW₃₀: 1.0 kg (0.9; 1.0)*. Median ∆ FFM when calculated based on actual BW, ranged from 0.1 kg (−0.1; 0.3 (p=0.005*)) at T₄₅ to 0.2 kg (0.0; 0.4 (p<0.001*) at T₃₀. Median ∆ FM ranged from 0.8 kg (0.6; 1.0 (p<0.001*)) at T₃₀ to 0.9 kg (0.6; 1.1 (p<0.001*)) at T₆₀. When BW₀ was used in the calculations, median changes in FM were 0.1 kg (-0.1; 0.3 (p<0.001*)) at T₄₅ to 0.1 kg (−0.1; 0.4 (p=0.005*)). at T₆₀.

Conclusion: Intake of 1L water has minimal impact on FFM. Although FM is substantially increased after water intake  as a result of increased BW, this effect is negligible when baseline BW is applied, making strict water restriction prior to BIA not necessary. Using morning BW is recommended for accurate FM estimation.

Disclosure of Interest: None declared