Going into Sunday's clash at Bournemouth, Lacazette has scored only eight times in the Premier League since arriving from Lyon.
Wenger said: “The first six months are always difficult. It is a difficult period the first year. I would say the physical pressure on strikers in England has become absolutely massive.
“The intensity in the challenges is much bigger than in France."
“It is normal," added Wenger. “In England you can play against teams who are organised and can physically cope with 90-minutes' intensity.
“The defenders have become much quicker than before – they are all athletes now at the back."