Ben Affleck has nothing but nice things to say about Jennifer Lopez as he praised her work ethic and wondered how she still looks as young as she did back when they were still a couple.

The "Batman" star called his ex-fiancée the "hardest working person" in showbiz in an InStyle magazine cover story about her. He admitted that he was "completely humbled and blown away by what she was committed to doing day in and day out."

Affleck praised "the quiet and dedicated way she went about accomplishing her goals, and then how she would go back and redouble her efforts." He also noted that Lopez "remains, to this day, the hardest-working person I've come across in this business."

"She has great talent, but she has also worked very hard for her success, and I'm so happy for her that she seems, at long last, to be getting the credit she deserves," he added.

Affleck and Lopez met on the set of "Gigli" in 2001 and got engaged from 2002 to 2004. The actor looked back on those years they were still a couple and could not help but compliment the 51-year-old actress on her ageless beauty.

"Where are you keeping the fountain of youth? Why do you look the same as you did in 2003 and it kind of looks like I'm in my best?" the 48-year-old "Justice League" star asked.

Lopez could only laugh in response as she called Affleck "funny." She also complimented him back when she pointed out that "he still looks pretty good too."

"I don't have any [beauty] secrets except JLo Beauty — and I'm giving them all to everyone with every product...I also think I'm in the best shape of my life. In my 20s and 30s I used to work out but not like I do now," she explained.

Lopez admitted that she does not work out more but "harder and smarter." She told the publication that she stays in shape not for her looks but more for her health as she acknowledged that "when you do things for the right reasons, you actually look better!"

Jennifer Lopez and Ben Affleck
Jennifer Lopez and Ben Affleck at the 2003 Oscars. REUTERS