New Delhi, April 15 (ANI): America's teenagers are replacing denims with elastic-waistband stretch pants called Leggings, according to a report on teens' buying habits.According to a semi-annual study released by financial services firm Piper Jaffray, leggings and yoga pants from Lululemon were ranked as the favorites among female teens this spring and Nike was the most popular trend brand among boys.A new term 'Athleisure' has been coined for clothes that can be worn outside the gym as well. The teen buying report also stated that denims were nowhere to be found on the list after constantly staying in top ten for several years.