The veteran lightweight turned down the option of an additional hour to cut.
Lightweight champion Ben Henderson actually weighed less than challenger Frankie Edgar, although that figures to change significantly by Saturday. Henderson (20-8) came in at 154.4 pounds. Edgar (14-2-1) weighed 154.6.
Despite being one of the smallest fighters in the division, Edgar won the belt in April 2010 and successfully defended it three times before falling to Henderson in February.
UFC president Dana White has made it no secret he would like Edgar to drop to the 145-pound division where a blockbuster fight exists with current champion Jose Aldo. Edgar, however, successfully lobbied his way into a rematch at lightweight.
"Dana thinks I'm a good fit at 145; he's been stressing that from day one," Edgar said. "But I'm strong and fast staying at 155 and I wanted the rematch.
"It's not like I had to beg him or anything. He wanted to let me know his reasons, I let him know my reasons and here we are."