Using a double-blind crossover trial ( Clinicaltrials.gov ID : #NCT 01477294 ) with two conditions ( 4-day each with a 3-day-washout period ) , randomly ordered as caffeine ( 5 mg/kg per day ) and placebo ( malt-dextrine ) intake , TEE was measured by DLW in 17 physically active men ( 20-38 years ) who were non-caffeine users .