Jaws dropped when Shania Twain took the stage on the London stop of her Queen of Me tour on September 16 — but it wasn’t because of her great performance or fabulous costumes. “People couldn’t believe how much weight she’s lost,” says an insider. “She credits it to staying healthy and sticking to a strict diet of mostly protein. Shania says she does it for energy.” Which the singer, 58, had plenty of during her two-hour concert. “She feels great. She won’t say exactly how much she’s lost, but she’s easily dropped over 20 pounds — some say it’s as much as 30. Whatever the real number is, she looks amazing.”