The 42-year-old star is romancing Casper Smart, 24, after meeting him on her world tour, on which he is a backing dancer.
The pair have been on several dates, including some nights out in Las Vegas, and the hunk has reportedly confessed to pals he and Lopez are spending most of their time in the bedroom.
A friend of the dancer told The Sun newspaper: "Casper said J.Lo has an amazing body and she`s in better shape than any other girl he`s ever been with. He said she`s got the body of a 20-year-old. They`re inseparable right now.
"It`s just about sex - and no one`s sure if it has much of a future. But he`s having a good time finding out."
At the moment Jennifer is said to be treating the relationship as a "fun fling" and is enjoying getting to know Casper.
A source said: "They are dating and having a good time. They`ve been getting more open with their flirting for weeks.
"It`s a fun fling. It`s not meant to turn into anything more."
Jennifer separated from her third husband Marc Anthony - with whom she has three-year-old twins, Max and Emme - in July.