London: Jennifer Lopez is all set to make a slender appearance in her judging debut on `American Idol` this month by shedding her curvaceous derriere.
The 41-year-old actress is training under Tracy Anderson, who was pop star Madonna`s ex-fitness instructor, reported Daily Mail.
Anderson`s celebrity clients include Hollywood actress Gwyneth Paltrow and Columbian singer Shakira.
"Jen is one of the hardest-working fitness fanatics in Hollywood and definitely has the discipline for Tracy`s tough regime. She loves the difference Tracy`s dance workout has already made," a friend said.
The `Maid in Manhattan` star liked what Anderson did for Shakira and wanted the same. Earlier Madonna had to got through extreme workouts with the trainer.
Lopez previously worked out with Gunnar Peterson, who got her back into shape after she had twins.