Lady Gaga hired a top Hollywood fitness trainer to help her develop the best body in pop.

The eccentric singer recruited Harley Pasternak last year after deciding she wanted to tone up.

Pasternak has appeared on numerous TV shows and trained the cast of the X-Men and Twilight movies.

And the Canadian fitness guru insists GaGa is a model client. He tells InTouchWeekly.com: "Like most stars she doesn't have a ton of time, so when she is with me she stays focused and never complains no matter how hard I push her.

"She has always been active, but about a year ago, she decided she wanted to have the best abs, legs and arms ever - so she stepped up her workouts."

Pasternak reveals GaGa was also motivated by the desire to look good in her trademark revealing stage outfits, adding, "Now she is super confident about her body and comfortable wearing everything and anything."