The Hawthorn vice-captain is playing at 87.5kg in 2013, down on the 89-90kg he carried onto the field last year.
Although not a drastic drop, Lewis said it had been enough to boost his running capacity.
"I'm feeling a lot better, and managing to cover the ground better," he told AFL.com.au.
"It's a bit easier than running around at 90kg."
However, Lewis said the change in playing weight had not been a deliberate focus over summer, and had a lot to do with end of year wrist surgery, which kept him away from weights and contested work for much of the pre-season.
"It wasn't planned," he said.
"It may have had something to do with [the surgery], no doubt.
"You obviously do a lot more running than physical contact. It just happened gradually over time."
The 27-year-old has been as consistent as ever this season, averaging 23.1 disposals and 4.3 clearances per game.
He said he had noticed an increase in the speed of the game over the opening nine rounds, thanks largely to the new rule requiring umpires to throw the ball up at stoppages around the ground rather than bouncing it.
"There is a lot more space than there was in the past, so the runners are really coming into the game," Lewis said.
"The game is definitely quicker.
"With the ball getting thrown up, there's less time to set up and less time to react."
While that has meant his own increased aerobic capacity has been useful, it has been even more advantageous for free-roaming types such as athletic wingmen Isaac Smith and Bradley Hill, he said.
"Players like Isaac and 'Hilly' can really break the game open, because there's a lot more space to run into," Lewis said.
