Sydney Sweeney's remarkable transformation into champion boxer Christy Martin can't fix the film's flaws nor distract from the star's real-life persona.

Sydney Sweeney trained for months, muscled up, and put on 30lb (13.6kg) to play Christy Martin, a real-life champion boxer with a dramatic personal story. She wears a dark wig and brown contact lenses. And yet it is impossible to forget that she is Sydney Sweeney in the cliché-ridden biopic Christy, as our hyperawareness of her off-screen image distracts us from what's going on in the film, which premiered at the Toronto International Film Festival this week.

A contradiction at the heart of Christy is that Sweeney is the main reason anyone is paying attention to the project, but her own high-profile celebrity makes it difficult to believe her as the character. Can she ever escape the real-life chatter around her?

The actress has been the centre of often unpleasant publicity, especially in recent months. There was a notable kerfuffle about her American Eagle ads, with the tag line "Sydney Sweeney has great jeans", which some took as a reference to Aryan genes. Then Donald Trump praised her for being a registered Republican. And The Hollywood Reporter wondered where her career would go "after being in the centre of the storm". That's not the kind of baggage any actor wants to be carrying on screen, but with Sweeney it's impossible to put aside right now.

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