Popp Dich schlank(2005)

Paul and Paula are partners in their profession as comic artists and best friends in their private lives. They also have the same problem: being overweight! When Paul's school sweetheart Mariah suddenly turns up and is about to move to the city, Paul decides to lose weight. But he breaks his leg during his first attempt at fitness. And how do you burn a lot of calories despite breaking your leg? By popping! The results are impressive and gradually everyone around him falls for the sex diet. Eventually even Paula, who persuades her good old friend Paul to have sex with her. After all, they know each other inside out and don't want anything else from each other, or do they?