What 'Brittany Runs a Marathon' taught Jillian Bell about body image

The instant Brittany O'Neill found out that a film about her life was going to premiere at the Sundance Film Festival, she started dieting.

The movie is, after all, a transformation story of how she'd gone from an unmotivated, out-of-shape 20-something to a healthy marathoner who finished the 26.2-mile New York City race in under four hours.

"The constant refrain with my friends became: 'I can't eat anything, I'm going to Sundance,'" O'Neill recalled. "I was like, 'I have to look like an "after" photo.'"

And when she flew to Utah last January for the debut of "Brittany Runs a Marathon," she had dropped a lot of weight - one pound away from the ideal number she'd long dreamed of seeing on the scale. But her thin frame wasn't received as positively as she'd hoped. Upon greeting Jillian Bell, the actress who plays her in the film, O'Neill was met with concern.

"I said something like, 'Hey, I adore you, and I don't know how to talk about