Zareen Khan and Karan Singh Grover are leaving no machine untouched in their gyms to make sure that they look their hottest best in Vishal Pandya's Hate Story 3.

An insider reveals that the two are gearing up to shoot some steamy scenes in the erotic thriller that requires them to show off their perfectly-toned bodies. And for it, the duo has taken to the gym with a vengeance. While Karan is already quite super fit with his well-toned abs, Zareen, who has always been under the scanner for her extra pounds, too has lost oodles of weight and is looking sexier than ever.