Jennifer Lopez doesn't need to diet as she works out so much.

The singing sensation has always rocked perfect curves and is often seen flaunting her figure in gorgeous red-carpet outfits. Trainer to the stars Tracy Anderson - whose other famous clients include Gwyneth Paltrow and Madonna - helps Jennifer, 46, stay in shape and insists there's been no tampering with her eating habits, as her exercise regime is so strenuous.

"No, she wasn't overweight anyway and she is a very healthy eater," Tracy told Britain's Closer Specials Diet & Fitness magazine. "She doesn't diet as she works out so much. I only get involved in people's diets if they are very unhealthy."

The fitness guru and Jennifer have worked together to create a series of workouts catered especially to the pop star. As for what areas the On the Floor singer focuses on most, Tracy revealed they give extra attention to her butt and legs.

"She has a beautiful shape so we wanted to keep that, but I designed a workout to keep her sexy butt toned and lifted and got her legs looking long and feminine with better skin tone," she said.

Tracy even shared the moves devised for Jennifer, explaining there's eight to 10 different leg movements which they repeat around 40 times each. When it comes to working her arms, sometimes 3lb (1.3 kilogram) weights are used, before the pair break into dance aerobics for 40 minutes.

Jennifer is so proud of her hourglass figure that she recently unveiled a tank top which she designed to celebrate women's curves. Sharing a snap of the white top on Instagram, which featured an old-school photo of her alongside the line "Lucky to have these curves", she urged her female fans to get one before they're gone.