Phiona Mutesi happened upon chess as a famished 9-year-old foraging for food in the sprawling and impoverished slums of the Ugandan capital.

"I was very hungry," says Mutesi, aged about 18.

Now a chess champion who competes internationally, her tale of triumph over adversity is being turned into a Hollywood epic with Oscar-winning Kenyan actress Lupita Nyong'o tipped to play her mother.

"My dad had died, and after the age of 3 we started struggling to get food to eat, my mum was not working," Mutesi says. They lived on one meal a day.

She was forced to drop out of school at 6 when her mother could not pay the fees.

One day, Mutesi discovered a chess program held in a church in the Katwe slum districts in Kampala. Potential players were enticed with a free cup of porridge, and Mutesi began organizing her days around this.

"It was so interesting," she recalls of her introduction to pawns, rooks, bishops, knights and kings in 2005. "But I didn't go there for chess, I went just to get a meal."

As she returned week after week, something unexpected happened that would transform Mutesi's life.

The young girl developed a talent for chess, which was only introduced in Uganda in the 1970s by foreign doctors and was still seen as a game played by the rich. And her talent turned into a passion.

"I like chess because it involves planning," says Mutesi. "If you don't plan, you will end up with your life so bad."

The film, entitled Queen of Katwe, is based on a book of the same name about Mutesi by American writer Tim Crothers. It is to be shot in Uganda and South Africa, directed by Mira Nair. Filming will reportedly begin in late March.

Coach and mentor Robert Katende, of the Sports Out-reach Ministry, remembers Mutesi wearing "dirty torn clothes" when he met her a decade ago.

"She was really desperate for survival," says Katende, who is building a chess academy to accommodate 150 students outside Kampala.

Two years into the game, Mutesi became Uganda's national women's junior champion, defending her title the next year.

"Phiona Mutesi has flourished," says Vianney Luggya, president of the Uganda Chess Federation.

"She made history in the schools' competition by becoming the first girl to compete in the boys' category. It was certainly surprising."

By the time she participated in her first international competition, Africa's International Children's Chess Tournament in South Sudan in 2009, Mutesi still had not read a book.

Since then Mutesi has competed in chess Olympiads in Russia's Siberia, in Turkey - after which she was given the Woman Candidate Master ranking by FIDE, the World Chess Federation - and in Norway last year.

The teenager, who has two more years of high school left, hopes to go to the next Olympiad in 2016 in Azerbaijan.

Luggya hopes the film will "open doors" for all players in Uganda, saying: "I think Ugandans realize that it is a brain game that can enhance their potential in all other aspects of life."

While Mutesi's goal is to rise to Grand master, she also hopes to become a paediatrician and open a home for children, especially girls facing the same predicament she overcame.

"But I don't think there's any reason why a girl cannot beat a boy. It comes from believing in yourself," says Mutesi.