India, Feb. 9 -- Jennifer Lopez has reportedly been a positive influence on her rumoured new man, Kevin Costner when it comes to fitness. According to an insider, the On the Floor singer's "incredibly fit" body and "eternally young" demeanour have inspired the Yellowstone star to step up his own fitness goals. The source revealed to InTouch that Lopez's commitment to staying in top shape has played a "big factor" in motivating Costner to focus on his health and wellness.

A source told InTouch, "She's among those inspiring him to hit the gym and prove age is just a number. Of course, it's going to take a huge amount of dedication, and not just in the gym but also in the kitchen."

They shared, "Kevin keeps himself pretty lean and healthy ...