The influence of coffee consumption on bioelectrical impedance parameters: a randomized, double-blind, cross-over trial

Background Bioelectrical impedance analysis (BIA) is a widely used method for estimating body composition. Avoiding foods/beverages containing caffeine is a frequently enforced pre-test protocol to ensure reliability of BIA measurements. However, few studies have evaluated whether this is necessary, with conflicting results. We aimed to determine whether the coffee consumption differing in caffeine content influences BIA parameters in healthy adults. Methods Twenty-five healthy adults were enrolled in a randomized, double-blind cross-over trial. Three amounts of caffeine were given with 200 mL of coffee: 0 mg (11 g of decaffeinated), 200 mg (5.5 g of caffeinated plus 5.5 g of decaffeinated), and 400 mg of caffeine (11 g of caffeinated). BIA measurements were conducted at 6 different times, and coefficient variations (CV) explored. Results No differences were observed for group x time interaction on impedance, resistance, or reactance (p > 0.05). Values of BIA parameters increased after 30-min of coffee consumption, independently of the caffeine dosage (all p < 0.001). Body fat percentage followed the same pattern and increased after 45-min (p < 0.05). Median CV for consecutive impedance, resistance, and reactance measurements were >95%CI of expected device measurement error over 70-min, without difference between groups. Urine output volume was not different between groups (decaffeinated: 440.45 +/- 197.57 mL; 200 mg: 471.80 +/- 171.88 mL; 400 mg: 489.30 +/- 204.10 mL, p > 0.05). Conclusion Coffee consumption influenced BIA-derived results after 70-min but was not related to caffeine content, likely due to water intake.