The CR Society members are lean but not abnormally thin. They would look at home in any picture from the 1950s when rationing meant few people could afford to be fat. The conference is partly social, but it’s also heavily scientific: this is a diet for geeks. After a talk entitled “Metabolic Effects of PGC-1a Overexpression in the C57B16 Mouse” I’m dreaming about coffee and Double Deckers – this lot are scribbling and even asking questions.

The camaraderie is good. I am probably eating too little, a few people warn. Rapid weight loss releases toxins into the body. I should be aiming for gradual weight loss, about 1lb a week, eventually aiming to be three or four points below my present BMI.

Most of the people are middle-aged and up. Health seems to be their first concern, then longevity. But for some it’s about a dream as old as mankind – escaping death.

David Fisher, who has flown over from Berkshire, says he had a fear of death from an early age. “I used to lie in bed worrying about it,” he says. There were no parental deaths to trigger his dread, no nasty incidents with Fido and a Ford. His fear of death is something he describes as “totally logical”. “Because aging happens over time, people don’t think about it until it’s too late. Maybe our only difference is an inability to put our heads in the sand,” he says. Within the next 30 or 40 years, Fisher’s convinced there is a 50/50 chance that the “problem” of ageing will be solved – and he’s determined to be around to see it. He’s dedicated to the task. He has been on CR for about 15 years and now eats 1,600 calories a day. He tells me he’s 50. He looks 40 or younger until I really start staring. Does he dye his hair? What about the eyelashes? But I’m being mean.

The fact is, he looks a lot healthier than me.

The CR community’s most dedicated mortality escapologist is Michael Rae. Six foot and 115lb, wearing baggy parachute trousers, Rae looks like a man from the future. He arrives in a T-shirt that reads “Immortal”, his milk-coloured skin so clear it looks airbrushed. His ears and fingers have a carrot-coloured hue – apparently caused by the amount of carotene he eats – enhanced by his ginger hair, so neatly combed you can see the lines the brush has left.

Michael carries a postal scale to weigh his food. He needs it. Other CRs wing it, guessing weights, reading the backs of packets, splurging now and again, and making it up the next day. Michael is hardcore. His regimen is 1,913 calories a day, every day: 30% derived from fat, 30% from protein, and 40% from carbohydrates.

Rae is a research assistant to Aubrey de Grey, the Cambridge scientist and Gandalf lookalike who believes technology is on the verge of conquering death. Together, they wrote Ending Aging: the Rejuvenation Breakthroughs that Could Reverse Human Aging in Our Lifetime. De Grey is not a big fan of CR. The effect is profound in short-lived mice, but in man, whose life is so much longer, de Grey believes CR’s effect will be minimal. “Long-lived species like us won’t get much, probably no more than a couple of years,” says de Grey. “Michael has some complicated but interesting criticisms of my argument, and the debate is very much ongoing. I should stress that I definitely don’t pooh-pooh CR – I think that even a couple of years is worth it if you’re the sort of person who can do it.”

“My argument is, where is his f***ing data?” says Rae, with a laugh. “The big question is, does it translate to the human case? If it didn’t, I wouldn’t look so goddamn skinny.”

Rae’s girlfriend, April Smith, is equally striking. Smith is CR’s top blogger and the couple are becoming the most public face of CR. Pale, with the same clear white skin as her boyfriend, April is thin but not thin enough for some. She tells me a very famous US TV show once called and asked if she would come on to talk about CR. After they had seen her picture, they cancelled. “They were looking for freaks,” she says. Another show cancelled after asking her about her “800-calorie-a-day diet”. When she told them she ate 1,300, and that if she ate 800, she’d be dead, they cancelled too. April is a martyr to the media. After an article featuring the couple appeared in New York magazine, April received death threats: “Die in a fire and do it soon.”

Perhaps it’s her libido that has this effect on people. CR has given her the sex drive “of a teenage boy” she says. Apparently, this is common in women. In men it often has the opposite effect, although April is all too keen to tell me she and Rae have a very active relationship. One married CR adept tells me he hasn’t had sex for two years. I assume he is blaming the diet.

There are sacrifices to be made for a CR life, as they are all happy to admit. Friends and family find your eating habits difficult to deal with. Wedding cake? No thanks. You feel the cold more (layering is big in CR land). Hunger is an issue and you are constantly bombarded by ads for food in a society where, as one CR-er tells me with a withering look, a man on the edge of chubby (cough) is seen as thin. No Double Deckers, no social life, no nookie and now I’m being insulted. Do I really want to live to 120?

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