True Stories: Thin
More4, 10pm

"I just want to be thin," said Alisa. "If it takes dying to get there, so be it."

A patient at Florida's Renfrew Centre for eating disorders, the pretty 30-year-old, a divorced mother-of-two, was one of a quartet of women at the heart of Lauren Greenfield's provocative film last night. Granted incredible access over six months, the director proved a sensitive confidant, producing a documentary that subtly questioned the facility's regime even as it showed the self-consuming desperation of its patients.

Such was the bond of trust between subjects and film-maker that Greenfield and her director of photography Amanda Micheli, who remained invisible and inaudible throughout, became privy to many intimate moments when the women contravened the centre's rules. Yet for the sake of her documentary, or perhaps some feeling of sisterly solidarity, Greenfield never grassed on anyone. In a situation where intervention might conceivably have meant the difference between life and death, it made for unsettling viewing in an already uncomfortable film.

Alongside Alisa - who seemed well-proportioned yet perceived countless bits of her body as requiring immediate cosmetic surgery, and who joined the air force during Desert Storm to lose weight - was Shelly, a bulimic 25-year-old with an inferiority complex concerning her twin sister. One of the most shocking moments in the film came when she hoisted up her T-shirt to reveal the abdominal tube she'd been feeding through for the last five years.

Incredibly, she'd started to expel food back through it.

Only mildly less disturbing was the family therapy scene, in which her father blamed his daughter's illness on moving to Utah. "They don't eat good food there," he lamented. "They eat vegetables."

The saddest figure in the film was15-year-old Brittany, whose group-session breakdown when confronted by criticism of her peers was heartbreaking to intrude upon. An overweight child who had been dieting since eight and had dropped from 185lb to 97 before her admission, Brittany had been encouraged to play bingeing and purging "games" by her mother, a fellow bulimia sufferer who appeared dangerously apathetic to whatever example she imagined she was setting.

Then there was the charismatic Polly, who had slit her wrists after just two slices of pizza. The Randle McMurphy of this cuckoo's nest, where the patients' rooms were habitually turned over to search for contraband drugs or discarded food, she eventually paid a high price for her persistent rebellion.

So close did Thin manage to get to the women - from the lobotomised mornings when they stumbled to their weigh-in, the results of which they were never allowed to know, to their various but sporadic moments of joy - that the documentary swiftly aligned to their perspective of enclosure, isolation and persecution. One in seven adolescent American females suffers from an eating disorder, we were told. But no attempt was made at a broader social critique or enquiry. Why, for example, is anorexia a developed country's disease, and why is it principally experienced by women rather than men?

Greenfield never acknowledged these questions, but she did allow herself an implied criticism of a medical system that returns these women into the world, ill-equipped, as soon as their insurance expires or their family can no longer foot the bills. On the outside, we saw a hesitant Shelly dining at a busy restaurant with the now beamingly self-confident Alisa. A few hours later, Alisa was distracting her children and dog so she could casually vomit her meal once more, seemingly unconcerned by the camera.

The film's ending came depressingly short of optimism, suggesting that the four will never completely overcome their illness. Thankfully, despite further suicide attempts, none so far has died. A follow-up film just five years hence would make for compelling viewing.