Russell Crowe showcased his dramatic weight-loss transformation as he enjoyed a rare family appearance at the Venice Film Festival. The Gladiator star, 62, was joined by his long-term girlfriend, Britney Theriot, 42, and his youngest son, Tennyson, 20, at the premiere of his self-directed documentary, What Love Builds, on Friday. Looking noticeably slimmer, Russell cut an elegant figure in a black dinner suit featuring satin lapels, which he paired with an open-neck white shirt and polished black shoes. © Getty ImagesBritney Theriot and Russell Crowe attend the 83rd Venice International Film Festival The Oscar winner wore his long hair swept back into a low ponytail, while his full silver beard completed his distinguished red-carpet look. Britney looked glamorous in a plunging black halterneck gown with a figure-skimming silhouette. She completed her look with sparkling drop earrings, a diamond bracelet and pointed black heels, while Russell affectionately wrapped an arm around her waist as they posed for photographers. Tennyson coordinated with his father in a black suit, patterned tie and crisp white shirt, adding a distinctive …