So, did Kevin Costner gain weight for The Highwaymen?
Viewers of The Highwaymen will definitely realize that Kevin looks practically unrecognizable in the film. And the reason for that is that he had to put on a bit of weight to play a convincing Frank Hamer in the film. “I saw it about 10 years ago, and I thought it was good then. But it didn’t fit what I was doing or thinking about [at the time],” Kevin revealed in a Vanity Fair interview about his initial decision to pass on the 2003 project.
But flash forward 15 years, and Kevin was ready to do whatever it took to tackle this role. “I knew to play him, I would have to put on 10, 12 pounds, and not be able to get over a fence,” he said. Kevin even managed to stay in character when his co-star Woody Harrelson, who Kevin describes as being “pretty big on health,” tried to get him to stray from his weight-gaining diet.
Source : https://www.distractify.com/p/did-kevin-costner-gain-weight-for-the-highwaymen