It's a tough job being best man, but is
Joe Jonas under strict instructions from brother Kevin that he has to be in peak condition for his upcoming nuptials?
Whatever the reason, Joe is turning into a true gym rat, pumping iron and doing cardio classes at his local fitness club in Toronto.
The Jonas Bros are in town filming a movie, and seemed to get mobbed by screaming fans wherever they go.
The guys are always happy to sign autographs though, making many ladies in the Canadian city very happy.
Check out buff Joe in the gallery below...
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