Passive dehydration-mediated body weight loss on body composition and phase angle in healthy men

Abstract

Purpose: To evaluate the effects of an acute weight loss due to passive dehydration on phaseangle (PhA) and body composition variables through bioelectrical impedance vector analysis(BIVA). Methods: Twenty-five healthy physically active males (22.6 ± 3.2 years; 76.7 ± 15.9 kg;172.0 ± 6.3 cm) participated in this study. Optimal hydration state was verified before intervention(urine specific gravity; USG < 1.020). Participants remained seated for 5 hours in a controlledtemperature room (26.6 ± 1.7°C; relative humidity = 72 ± 4.9%) with no consumption of food or water.Subsequently, the participants entered a room at 21.8°C and 38% of humidity, and removed theirsweat excess with a dry cloth. Heart rate (HR) and tympanic temperature (TyT) were recorded afterthe participant lie down in supine resting for 10 min while an octopolar bioelectrical impedanceanalyzer (InBody 770) was used to record Xc, PhA, fat mass percentage (FM), skeletal muscle mass(SMM) and total body water (TBW) before and after the intervention. Frequentist inference (pairedt test), estimation statistics (Hedges’ g) and BIVA analysis (RXc plot) were utilized to compare pre-post changes. Results: Significant differences were found in body mass (Δ = -0.76 kg; p < 0.05; g = 0.046), HR(Δ = +10.4 bpm; p = 0.001; g = 0.89), FM (Δ = -1.0%; p < 0.01; g = 0.15), and PhA (Δ = +0.09°; p = 0.005;g = 0.15). No differences were found on TyT (Δ = 0.0 °C; p = 0.360; g = 0.0), SMM (Δ = +0.08 kg;p = 0.553; g = 0.01), and TBW (Δ = +0.18 L; p = 0.193; g = 0.02). The analyses of 95% confidenceellipses in the RX c graph showed overlapping for most body segments although a trend forseparation between pre-post values was detected in lower limbs. Conclusions: A small change on body mass due to passive dehydration altered BIVA outcomeswhich resulted in significant changes on PhA and FM in physically active men.