The problem with Dennis, the 'fat boy' of the title, is exactly that. What is his problem? He's a loser, a scumbag and utterly unlikeable, and at no point in the film does he become a nice, likable, or sympathetic character. So it is very hard to root for someone this self-involved. At no point is he ever nasty or pathetic in a funny way, he's just a jerk. And no matter how many 'emotional' scenes are rammed in, it has been five years since he left his pregnant fiancée at the alter. FIVE YEARS of seeing her every day. How is it only NOW that he wants to do anything about it? And it doesn't matter if he does. It's been FIVE YEARS. It's too late. Luckily for him, the people he wants to win back, the dull Libby and their duller son Jake, are so flat, the audience can't care about them either. Especially Jake. And the lazy demonising of Libby's new love Whit is obvious and convenient so Dennis can worm his way back in to Libby's affections after five years of being the most detestable and unreliable jerk she could hope to meet.<br /><br />So, Run Fat Boy Run isn't funny. There are a couple of jokes that possibly could have worked as part of a sitcom, but never in a one-off film, but just to make it clear, this isn't funny. The serious scenes are even worse, falling horribly, uncomfortably flat, and the painful dragging out of a heart-warming ending is not heart-warming. There is no character development or motivation, so basically there is nothing here that is needed to make a film. Dire.