Gatland is currently preparing for Wales' first warm-up game against England at Twickenham on Saturday, with two more fixtures to follow before the tournament.
England will travel to the Millennium Stadium one week after the Twickenham clash and Wales will then face Argentina at home on August 20.
While the big three southern hemisphere team will go into the tournament off the back of a full Super Rugby season and Tri-Nations competition, Gatland hopes his side's fitness work will also stand them in good stead.
"The southern hemisphere teams will probably be a little bit better prepared, in terms of the game time that they will have had together," Gatland said.
"But hopefully we've got the physical preparation done as well in terms of having what is almost like a pre-season - we've had a little bit of a break and we've been able to do the work in the gym.
"(There has been) some quality time spent together as well, which you don't usually get."
But centre Jamie Roberts says that all the work in the gym will count for nothing if Wales, who finished fourth in this year's Six Nations table, cannot produce the goods when it matters.
"We all know that on the pitch is where it counts," Roberts told Sky Sports News.
"You can train as hard as you like but all of us as individuals, and collectively as a team, need to show what we can do on the pitch.
"There's no point being the fittest guys in the world if we're not good rugby players, we are well aware of that."
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