Ryan had lap-band surgery at NYU Medical Center, and was relaxing at his home in New Jersey on Saturday night, team spokesman Bruce Speight told The Associated Press.
Speight said Ryan also had a hernia repaired.
The outpatient procedure came a day after Ryan and the Jets wined and dined free agent running back LaDainian Tomlinson, trying to persuade him to join the team that had the league's No. 1 rushing offense last season.
The 47-year-old Ryan has frequently poked fun at himself and his rotund midsection, including after unflattering belly bearing photos of him changing into a jersey during a Florida-Carolina NHL game last month floated around the Internet.
"I'm watching ESPN and I'm like, 'Whoa, that's not a real good shot,'" Ryan said during the NFL Scouting Combine. "I mean, don't get me wrong, I get hit on all the time by women."
"I think I was too fat," Ryan said with a laugh in December.
Ryan weighed 340 pounds at the start of last season, gaining at least 30 pounds after he was hired by the Jets in January 2009. He even tried a liquid diet during training camp and lost 20 pounds, but quickly gained it right back.
In a lap-band procedure, a plastic band is inserted that encircles a patient's stomach, effectively shrinking it and curbing their appetite.
Copyright 2010 by The Associated Press