German international Ozil has been an important figure for the Gunners this term, despite entering the final year of his Emirates contract and being linked with moves to Manchester United and Barcelona.
Ozil has made 10 Premier League appearances so far this campaign, scoring one goal and assisting three others.
"Mesut Ozil has worked hard and he's extremely fit at the moment, that's why you see him sharp," Wenger told Sky Sports News.
"The quality of his technical aspect is always there but he has added a more determined attitude and that's what you want from him and great players.
"Football today is very demanding on the mental and the physical aspect. Mesut today is in a much better shape than he was before."
Arsenal face a trip to Turf Moor to face Burnley this weekend after making a full set of changes in their defeat to FC Koln on Thursday.