Amiable. Bland. Cute. Formulaic. Inconsequential. "Run Fatboy Run" is all of these things, a middle-of-the-road confection that isn't sure whether it wants to be a gross-out comedy, a bittersweet love story, or an inspirational sports tale. Director David Schwimmer (yes, of TV's "Friends") demonstrates a light touch behind the camera that keeps the material from going too broadly over-the-top. When it does waver toward the silly, it usually fails tremendously, as in a misbegotten scene where a character's profanity is bleeped out in order to keep a PG-13 rating. This horrible editing decision puts a damper on things for minutes after, and is plainly tacky besides. What screenwriters Simon Pegg (2007's "Hot Fuzz") and Michael Ian Black do inject into the proceedings is an accurately captured real-world humanity to their characters. It is this layer that keeps the film from spinning out of control or growing monotonous.

é It has been five years since Dennis (Simon Pegg) ran out on pregnant fiancée Libby (Thandie Newton) on their wedding day. If time heals all wounds, then half a decade isn't enough for Dennis. Working as a security guard at a women's clothing store and having gained a few pounds in the interim, he is an out-of-shape lug, devoted to young son Jake (Matthew Fenton) but unable to come to terms with the mistake he made in abandoning Libby. When she gets a serious new boyfriend in the health-conscious Whit (Hank Azaria), Dennis makes it his mission to participate alongside him in an upcoming 26.2-mile marathon. "You've never finished anything in your life," a skeptical Libby tells him, but Dennis is determined this time to follow through with his goal and hopefully win over the women he still loves in the process.

When "Run Fatboy Run" gets released on DVD or finds its way to cable, watching it will be a painless and perhaps even enjoyable way to kill a few hours. Seeing it on the big screen, the film is of the take-it-or-leave-it variety. Humor is definitely on the weaker side; laughs could probably be counted on one hand, and certainly do not include a strained bit involving a naked Whit in the gym locker room, or another scene where Dennis and sparring best friend Gordon (Dylan Moran) duke it out on the street. A set-piece concerning a pus-filled blister is not for the squeamish, but would be right at home in a previous film starring Simon Pegg, 2004's "Shaun of the Dead."

If "Run Fatboy Run" were only existing on this one level, it would be a big bust. Fortunately, the characters of Dennis and Libby are written with enough care and empathetic attention to detail that it doesn't matter if it's a "funny" movie. Dennis, responsible for the break-up, is full of insecurity and believed at the time that he didn't deserve someone as special as Libby. Training and running in the marathon, then, is not merely a flimsy way to get Libby back, but, more important, is symbolic of his own self-worth. If he goes through with the race and manages to complete it, then maybe it'll be a sign that he's been underestimating himself all along. Dennis' journey to righting the wrongs of his past and becoming a better person is where "Run Fatboy Run" gets its heart, if not its innovation, and the ending is appealing in the way a hopeful denouement is reached without everything wrapping up in a neat bow.

Simon Pegg doesn't exactly scream out as a romantic lead, but he is well-cast and likable as the slacker-ish Dennis. He also shares a comfortable chemistry with Thandie Newton (2007's "Norbit"), lovely but arguably too talented for the part of Libby, who takes a long time recognizing that Whit is all wrong for her. As Dennis' and Libby's precocious son Jake, newcomer Matthew Fenton is exceptionally natural and charming. The rest of the characters are little more than sitcom types, from Dennis' womanizer friend Gordon to Dennis' bumbling overweight superintendent Mr. Ghoshtashtidar (Harish Patel). They're too cutesy for their own good.

"Run Fatboy Run" goes down with ease, but it's awfully slight. Effectual moments compete for screen time with interludes that feel like bad skits, and none of the above are quite able to escape conventions found in every romance or underdog story that have come before it. Recommending that viewers rush out to see it in theaters is a tough sell, but on video its underlying charms may help to make its numerous flaws and overall unremarkable impression more palatable.