Jeremy Allen White is revealing one major influence on his buff transformation for the upcoming "Iron Claw" movie ... telling TMZ Sports his co-star Zac Efron helped whip him into wrestling shape!!
JAW is playing Kerry Von Erich in the project about the famous Von Erich family ... and while he was never in bad shape by any means, the dude really bulked TF up for the role.
In fact, he didn't shy from putting his swole figure on display .