Author Mike Buchanan was never a fat boy, but he can relate.

The Alpharetta resident is transforming his latest novel, “The Fat Boy Chronicles” into a movie being filmed in Newnan. Tin Roof Films, where Buchanan is a partner, began filming last week, and Buchanan said he hopes to release the film sometime next year.

Buchanan, who was taunted some in high school, said he can empathize with his main character, Jimmy Winterpock, an overweight ninth grader. The novel, written as a journal, is from Jimmy’s perspective as he tells about being taunted and feeling lonely.

“I had funny glasses, and people picked on me about that,” Buchanan said. “And I grew up on the countryside where there weren’t a lot of people around, so I know what isolation feels like.”

Buchanan and his co-author, Diane Lang, got the idea for the novel when a man approached them at a book signing.

“This man came up to us and told us that his son did something really cool,” Buchanan said. “He was tired of being ridiculed for being overweight, so he lost 60 pounds one summer.”

Buchanan and Mrs. Lang decided to start writing together when they were both teaching at Chattahoochee High School. They were on a student scuba diving trip in South America when Buchanan let Mrs. Lang read the journal he kept about what he saw on his dives.

“It was very metaphorical,” she said. “We figured out that we both liked to write and decided to write a love story together.”

Since then, the pair has written four books and three screenplays. Mrs. Lang said she and Buchanan hope for a theatrical release for their film, which includes a cameo from “Varsity Blues” star and Kennesaw native Ron Lester.

The writing partners, who use the pen name Lang Buchanan, decided to convert the novel into a screenplay when they realized the impact it could have on a larger audience.

“The theme of the movie is that we’re all connected by the fact that we all have issues,” Buchanan said. “We all have to deal with something, so anyone could relate to Jimmy.”

“The Fat Boy Chronicles,” published by HiDef Media Group, is available at www.amazon.com and Barnes & Noble.

The duo has also taken their act on the road, giving lectures about childhood obesity at middle schools.

Information: www.tinrooffilms.com