Way to go, Mr. Costanza! After just four months, Seinfeld alum Jason Alexander is down 30 lbs. — and he’s showing off his new spandex-ready body to fellow Jenny spokesmodel Valerie Bertinelli in this hilarious new commercial, hitting the airwaves today.

The portly actor, 50, signed on as a Jenny spokesman in January with a starting weight of 195 lbs.