We had some problems due to a language barrier, and the safe word use could definitely have benefitted from a clearer explication at the start. And the GM has actually very little control on the pacing or the tone, once the game starts. Therefore, I concentrated on running scenes for escalation, a trick I've tried to hone when organizing Nathan Hook's excellent "Black Dog" several times before.
While I don't consider the run a complete success, we had some great moments (feel free to steal, should you run it somewhere). Mikko Pervilä did a great job increasing his level of sloughing, as the Fat Man, creating a palpable atmosphere of tragedy. Peter Adkison came up with a really powerful scene where the Fat Man passes his favorite restaurant after two successful days of dieting. A phone call between a skinny brother and the Fat Man who had just been rejected from a flight (as too big for a seat) to their father's funeral was really distressing, as was a job interview where he was promised a job - if he'd ever drop under 85kg. FMD is one of the games that makes you feel really bad about laughing, even as you can't avoid doing so.
More experiments with it are definitely needed. Even at moments when it did not really work, I could feel the inherent potential in the script.