THE fate of Troy teeters in the balance. The period epic starring Brad Pitt opened at No 1 at the US box office with an estimated weekend take of $45 million. For a modern blockbuster this has to count as a flop, unless it shows the same stamina as, say, Gladiator.

Four years ago Gladiator opened with $34 million, but thanks to solid reviews, Russell Crowe’s Oscar buzz and excellent word of mouth, it stayed afloat all summer, ending with a total of $187 million.

Troy lacks these qualities, so the pressure lies on the drawing power of Brad Pitt’s torso. Lord knows, no one is going to see the film for his attempt at a classical accent.

The summer’s first break-out indie hit looks to be Super Size Me, a $300,000 documentary shot on video by Morgan Spurlock about his experiment of eating nothing but McDonald’s fast food for a month. This “tongue-in-cheek and burger-in-hand” film became the most talked-about movie at the Sundance film festival earlier this year.

This was partly because the film takes a nod from the Michael Moore school of agit-prop and wraps its indignation in a (wholegrain) sesame bun of humour. It was also partly the result of perfect timing. Obesity had just exploded on to the front pages and, six weeks after the film’s debut at Sundance, McDonald’s announced the withdrawal of its Super-size menu as its “contribution” to the nation’s health.

In the 1980s the film shown to teenagers as shock treatment against trying drugs was Christiane F, about heroin addicts in Germany. In the next decade that position could be filled by Super Size Me.

The statistics it rolls out are sobering, even to anyone who has read Fast Food Nation. Two in five children and two in three adults now suffer from obesity in America. One in ten develops diabetes. People who develop the disease before the age of 17 lose on average 17-27 years of their life. Perhaps the most shocking sight is the serving of fast food in school canteens to waddling teenagers.

Spurlock’s own regimen offers graphic proof of the drawbacks of fast food. During his one month of McDonald’s, he piled on 25lb (11.3kg), developed headaches and depression, lost his sex drive and turned his liver into “pâté”.

His vegan girlfriend was scared for his wellbeing. All of his doctors admitted to being shocked at the rapidity of his decline. “I thought alcohol could have this effect, but not fast food,” says one. “Your cholesterol reading is obscene beyond words. You have to stop.”

The surprise is that Super Size Me is going into multiplexes that offer an overpriced dietary nightmare. It feels even more like heroic counter-programming when you realise that about 30 to 40 per cent of a multiplex’s income — all its profit, in effect — comes from food sales.

These days movies might as well be about clowns or pop singers as far as the theatre owner is concerned. Movies are a loss leader, a necessary expense in luring people into the foyer to buy food and drink. Is it any wonder, then, that since this shift in the business, films have evolved to appeal to the demographic group that eats the most foyer junk food — teenagers?