( CM ) - JENNIFER LOPEZ is wasting no time in getting back in shape after giving birth to twins - she's rehired her old trainer GUNNAR PETERSON to help her lose the baby weight. The singer/actress gained more than 50 pounds (22.6 kilograms) during her pregnancy but already appears to have shed much of the weight gain, judging by photos of the new mum on her first night out in New York since giving birth on 22 February (08). Lopez has reportedly installed a $50,000 (GBP25,000) home gym in her Long Island, New York mansion, according to In Touch magazine, and Peterson, who trained Lopez through the early stages of her pregnancy, is on his way to help her regain her fit and toned body. He says, "Her main priority is the health of the babies, so she'll start as soon as she gets the mommy routine down."