Is Calorie Restriction the key to Physical Longevity?

Note: I am posting this long piece – perhaps too long – in practice section because diet is really a form of practice.
This piece is good because it takes you inside this form of CULTivation. It also raises philosphical issues that intersect with Taoist practices designed to create longevity. The focus here is on physical “immortality”, not soul or spiritual immortality. It run parallel to the Kurzweil nono-immortality theme that wants to fix things physically to achieve long life.
My general take is that these folks are obsessive, indicataing some possible imbalance in their Yi/spleen/stomach shen. That it is much healthier if calorie restrictions comes spontaneously AFTER you’ve boosted chi-intake, which reduces the struggle amongst the five shen for energy on a calorie restricted diet.
I find that at home, where I am in my “own earth” and the space is attuned to me and I to the space/elements – that I need very few calories to feel great. When I am travelling, I see that I spontaneously eat more, my shen feel the earth there is not as awake and not feeding them in the same way. Or possibly the extra food is used to ground the group chi.
One good point raised in the piece is the danger in long fasts to your heart muscle, which can deteriorate. This is generally why Chinese medicine (and many Taoists) don’t do long fasts – it is considered to consume/burn your jing level in order to feed your chi functions. Only if you have learned to “eat” chi directly does bigu (“no grains diet”) become safe. There are two good essays on this topic in Livia Kohn (editor) Daoist Body Cultivation.
-Michael

Its followers claim that it boosts your sex life and makes you live longer. Julian Dibbell tries Calorie Restriction, the world’s most extreme diet

Super Skinny Me
Sunday December 3, 2006
The Observer

It’s 7.30pm in SoHo in New York, that magic hour when a grown man’s fancy turns to thoughts of food. My own thoughts, at the moment, are of practically nothing else. Half-sprinting through the crowds, I am late for a dinner party I’ve been planning for weeks, and I’m starving.
I’ve been starving for the past two months, actually, and that’s precisely what the party is about. My dinner guests – five successful urban professionals who for years have subsisted on a caloric intake the average sub-Saharan African would find austere – have been at it much, much longer, and I’ve invited them here to show me how it’s done. They are master practitioners of Calorie Restriction, a diet whose central, radical premise is that the less you eat, the longer you’ll live. Having taken this diet for a nine-week test drive, I’m hoping now for an up-close glimpse of what it means to go all the way. I want to find out what it looks, feels, and tastes like to commit to the ultimate in dietary trade-offs: a lifetime lived on the brink of starvation, in exchange for the promise of a life span longer than any human has known.

Seat belts, vaccines, clean tap water, and other modern miracles have boosted average life expectancies, to be sure, but CR alone demonstrably raises the maximum life span. In lab studies going back to the Thirties, mice on limited diets have lived as much as 50 per cent longer than the oldest of their well-fed peers – the rodent equivalent of a human life stretched past 160. And it isn’t just a mouse thing: yeast cells, spiders, vinegar worms, rhesus monkeys – a menagerie of species has been shown to benefit.
Despite the mounting evidence, however, the link between CR and longevity remained for many years a medical curiosity, its implications for human health intriguing but unexplored. Partly this was because nobody, to this day, has figured out exactly how the CR effect works. Some have suggested that the threat of starvation triggers certain self-preservative responses in animal physiologies; others have pursued a ‘fuel-efficiency’ hypothesis, proposing that lightening the body’s load of food-energy processing reduces wear and tear. But no theory has ever settled the question firmly enough to prove that humans would benefit from CR as much as other animals. That has left direct experimentation as the next best route to an answer, and for obvious reasons, finding human subjects willing to live on concentration-camp diets has historically been tricky.

In 1991, however, the proposition was simplified when eight bioscientists sealed themselves up for a two-year stint inside a giant, airtight terrarium in the Arizona desert – and discovered that the hypothetically self-sustaining ecosystem they’d settled into could barely grow enough food to keep them alive. This revelation might have doomed the experiment (known as Biosphere 2) but for the fact that the team’s physician, UCLA pathologist Roy Walford, had been studying the calorie-restriction phenomenon for decades and convinced his fellow econauts that – as long as they all ate carefully enough to get their daily share of essential nutrients – a year or two of near starvation wouldn’t hurt. When at last the Biosphere 2 crew emerged from their bubble, tests proved them healthier in nearly every nutritionally relevant respect than when they’d gone in. Fifteen years later, Walford’s CR primer, Beyond the 120-Year Diet: How to Double Your Vital Years, is in its fifth printing, and an estimated 1,400 people have taken up the diet as a full-time, lifelong practice.

It isn’t hard to see the appeal to a certain New York type: you’re skinnier than any social X-ray, you’re practising a regimen as extreme and gruelling as any yogi’s, and you’ve got medical science on your side. For someone attracted to control, accomplishment, and power, this is the life.

The hardest part is the maths: not just the labour of tracking everything I put in my body but the way calorie-counting makes the no-free-lunch adage so viscerally clear. Bacon cheeseburgers, chocolate, a martini – all are pleasures now ruined by the knowledge that the caloric debts that they create must be paid for with days or even weeks of cutbacks. Other abnegations are met with the compensatory feeling one gets when walking a righteous, if lonely, path.

So I’m thrilled to meet five newfound fellow travellers when I burst into the kitchen of a white-walled caterer’s loft I’ve borrowed for the occasion of my dinner party. Each of my guests is prominent among the CR movement’s hard core: Paul McGlothin, a 58-year-old Manhattan-based ad exec and volunteer director of research for the non-profit Calorie Restriction Society; Paul’s wife, Meredith Averill, 60; April Smith, a 32-year-old Philadelphia union organiser and author of April’s CR Diary, a highly readable and (within the CR community, at least) widely read online journal of her calorie-restricted life; her Canadian boyfriend, Michael Rae, a research assistant to life-extension guru Aubrey de Grey and a prolific, authoritative presence on the CRS mailing list; and Donald Dowden, a midtown lawyer and CR poster boy. There’s no mistaking the lean little crowd gathered here, and the recognition is mutual. Paul, blue-blazered, grey-haired, with the face and gaze of a preppy Don Knotts and the approximate body-mass index of a Noguchi floor lamp (5ft 11in, 137lb), gives me a once-over and grins. ‘You look,’ he says, ‘like one of us.’

‘I’ll take that as a compliment,’ I think. The 1,800 daily calories I’ve been consuming fall well short of the minimum 2,500 recommended for adult males, and two months on this caloric budget has shrunk my 43-year-old, 5ft 11in frame from an almost officially overweight 178 pounds to a high-school-era 157. Friends and loved ones have started sounding more concerned than impressed when they see how much weight I’ve lost, but here within the charmed circle of tonight’s dinner party, I don’t feel so much scrawny as trim – dashing, even.

Though I’m our official host, it’s the compact, wisecracking April Smith who presides. April has volunteered to plan and cook tonight’s CR-correct menu, and her sous-chef, Michael, stands beside her at the ready: a boyish-looking 35-year-old with brush-cut red hair, translucently pale skin, and – at 6ft tall and 115lbs – an eerily spare physique.

Divide Michael’s weight by the square of his height and you get a body-mass index of 15.6. Compare that with the minimum BMI of 18 recently decreed by the organisers of the Madrid Fashion Week – who cited the WHO’s definition of 18.5 as the lower limit of healthy weight and offered medical assistance to any models who couldn’t meet it – and you might wonder how Michael can stand up in the morning, let alone jog 20 miles a week. But jog he does, and if the results of both his latest physical and the latest CR research are anything to go by, he is probably one of the healthiest 35-year-olds on the planet.

‘Michael, could you hand Don the rocket?’ April calls, looking up from the laptop that’s always near to hand as she cooks, loaded with an interactive diet-planning program that helps not only count calories but track the 20 other nutrients without which CR would just be a glorified form of anorexia. ‘Don, I need you to put 24 grams on each plate, please.’ And so Don Dowden, attorney at law, commences weighing rocket on an electronic postage scale, adding a leaf here, removing one there, like a drug dealer parsing out dime bags. Tall, dark-haired, craggy, Don gets by on a ration of about 2,000 calories a day and swears by its rejuvenating effects. ‘I used to wear glasses, but I don’t any more,’ he says. ‘I don’t have 20/20 vision, but I can drive, and I can read the paper, and I’m 74.’

‘You’re 74 years old?’ I blurt, not so much astonished as simply confused. It’s not that I can’t see Don’s age in his face and skin, now that I know to look for it. But there’s something in the way his body moves, the way he holds it – an ease and an assuredness – that doesn’t quite square with the fact that he was born before FDR took office.

‘He gets that a lot,’ says Michael, a trace of glee in his otherwise quiet, clipped, north-of-the-border tone. April has him chopping asparagus now, while she crunches numbers. Tonight’s calculations are based on Michael’s caloric requirements, and those requirements are as strict as they come. Unlike April’s daily average of about 1,300 calories, which really is an average (she likes to go out drinking and dining with friends on weekends), Michael’s regimen of 1,913 calories a day is exactly that, with 30 per cent of them derived from fat, 30 per cent from protein, and 40 per cent from carbohydrates.

‘Michael’s dinner is always 639 calories,’ April explains, eyes on the screen while her fingers dance across the keyboard, tweaking portions. She makes the job look easier than it can possibly be. ‘I’m so used to doing this now. If I need more protein, I add more protein. If I need a little bit more carb, I add more strawberry. Ohhh, and I forgot the ricotta for the dessert… see? Now I have to mess with it. So 45 calories of non-fat ricotta, so I have to take out some protein, so I need to take out another scallop from the salad. Take out some strawberries from the dessert… What’s half of 90? What’s 90 plus 45? 135. Now we’re a little low, so add a bit more fat. See? Isn’t that beautiful?’

April turns the laptop to show me her numbers and yes, God help me, I do see the beauty. Though the full apparatus of scales and software isn’t a mandatory feature of the calorie-restricted lifestyle, I’ve been using both, and I know only too well the virtuosity it takes to throw together a perfectly balanced 639-calorie meal plan on the fly.

April seems happy with my accounting skills. ‘We’re so proud of you,’ she says as I rattle off my scores. She’s also pleased to hear that a tip she wrote up in the CR Society newsletter – start the day with a big protein load to head off afternoon carb cravings – has become part of my routine.

But, she adds: ‘You’re losing weight too fast.’ She talks with the crisp authority of a doctor handing me some bad but easily remedied news. ‘You’ve lost 20 pounds in two months, and you probably shouldn’t lose more than five pounds a month. You need to start eating more.’

This appears to be a cue for the evening’s two alpha geeks – Paul and Michael – to launch into mini-lectures on the biophysics of rapid weight loss. ‘When you do CR, you’re not just losing fat,’ Michael explains. ‘You’re losing muscle and bone.’ Shed weight too fast, and you can shrink the most important muscle you have, your heart, running the same risk of cardiac arrest that makes anorexia so dangerous. ‘Yeah, sure,’ Paul jumps in, ‘but the real thing is your immune system.’

A sixth guest arrives: my friend Adam, whom I’ve invited along for a variety of reasons, including his outside perspective and his promise to bring wine. It’s a Pinot Noir, per April’s request – the grape of choice for the calorie-restricted set, rich in anti-ageing resveratrol – and she has Adam fill our glasses with exactly 74 calories’ worth. Well, some of our glasses. Paul and Meredith practise a one-meal-a-day variety of CR, and it so happens they already ate. ‘Cheers, anyway,’ says Paul, quite cheerfully, as he and his wife raise their glasses of water with us.

We move to the table, which April has set with the salad course: the aforementioned 24g of rocket per plate, dressed with lemon juice and cushioning a couple of scallops sautéed in garlic, white wine, and coriander. We begin to eat, and I experience a culinary epiphany: sickened by the taste of scallops for my adulthood and afflicted, for as long as I can remember, by an aversion to coriander, I find myself now tucking into April Smith’s coriander-infused scallops-and-rocket salad as if it were the best salad I have ever tasted. And I’ll be goddamned if it isn’t.

‘Your sense of taste really does become enhanced when you’re hungry for your food,’ Michael observes. ‘You appreciate it more.’

Paul McGlothin sits to my right before an empty place setting, nursing his water and praising the food on the table almost as if it were on its way to his own mouth instead of everybody else’s. ‘Looks great! Smells great!’ he gushes. ‘Just watching you guys eat and smelling it, I know that tomorrow, when I break my fast, it’ll just be great. It’ll be terrific!’

There is no mistaking the manic gleam in Paul’s eye, and as I contemplate his peculiar fervour for the food he isn’t eating, I am brought face to face at last with a question that’s been taking shape within me from the moment I met him: dude, are you high?

I don’t put the question to him in quite those terms, but his answer, basically, is yes: he is high, and chemically so. ‘When you fast for 17 hours at a low glucose rate, brain-derived neurotrophic factor is released, which is a chemical which creates optimism,’ says Paul. ‘This brain-derived neurotrophic factor is actually a natural part of the chemical thing that happens to me every day… I feel pretty exhilarated right now.’

I believe him, but only because I’ve felt something like it myself. From mystics to anorexics, people who go for long periods without eating often report feeling more awake and energetic, even euphoric. It’s nice for a while, but even the calorie-restricted can get too much of it. When April started CR, she often went long stretches between meals and eventually decided something was a little off. ‘It makes you feel like you’re on drugs; I got too euphoric,’ she says. ‘You know, thinking you’re in love when you’re not.’ She switched to a more consistent, balanced eating schedule, and came back down to earth.

April brings the main course: asparagus tips, shiitake mushrooms, and the featured ingredient, an unlikely hybrid of life-giving wholesomeness and bio-industrial hubris known as Quorn.

Quorn, at last! For as long as I’ve been following the blogs and mailing lists of the CR community, I’ve been reading about this patented wonder morsel, perhaps the ultimate in CR-friendly foods. Grown in fermentation tanks from a cultured strain of the soil mould Fusarium venenatum, Quorn in its virgin state is almost pure protein and very low in calories. Processing adds various essential nutrients, including zinc, which is concentrated in almost no other food but oysters and which the calorie-restricted can never get enough of. The end product tastes and chews like an unbreaded Chicken McNugget and can substitute for meat with the versatility of soya yet with fewer saturated fats and none of the alleged dementia-and/or-male-aggression-causing properties.

Bellies beginning to fill, our attention turns now to a topic that has hovered at the edges of conversation all evening: sex and the CR couple. Of all the physiological inconveniences known to face the long-term calorie restricter – chills, stamina deficits – none strikes dismay into the heart of the initiate quite like CR’s potential to squelch libido. The diet has so far spared me that particular side effect, but I’m eager to hear from the present company what CR has done to their sex lives.

‘Michael and I have more, better sex than all of you combined,’ April announces. ‘Ha! Speak for yourself,’ Meredith retorts, seconded by her husband: ‘Not a problem in our household.’

Or in most calorie-restricted households. Not everybody on CR complains of lessened sexual desire, for one thing, and none of those who do, it seems, are women. Nor are the reported side effects as bad as what the ‘normal’ ageing process does to midlife sexual function. ‘Meredith and I are in our late fifties,’ says Paul, ‘and we do know the sexual habits of people our age.’ The calorie-restricted middle-aged couple likely doesn’t have the clogged arteries, sluggish endocrine systems, and other buzz-killing problems that conspire to extinguish many an older couple’s sex life.

All the same, says April, ‘it’s not entirely a myth’: CR can do strange things to the male libido. And she tells us what is probably the CR community’s best-known love story – her own.

‘I met Michael at CR3 [the third annual Calorie Restriction Conference], in Charleston, but I stalked him for eight months before that,’ says April. She was an avid reader of the CR Society mailing list and, in particular, of Michael’s postings. ‘I loved his writing. I developed a huge crush on him, and just assumed he was probably 57 and married. But eventually I saw a CBC interview with him about CR and saw that he was close to my age, and cute. The interview showed him in his house making his stir-fry all by himself. So I thought I’d capture him and take him to my country. We’re closing on our house on Friday.’

‘Before CR, I was hornier than most men,’ says Michael. ‘But some people find that, when they go on very severe CR, their classic male libido – that sort of aaaargh-there’s-a-pretty-woman-I-can’t-stop-my-neck-from-moving libido – goes down.’ And Michael, it turns out, is one of those people.

‘I’ve often thought that if you could explain to women that, on CR, men will improve their sexual performance but decrease their skirt-chasing, women would be like, “I’m cutting your calories, honey. Half your dinner tomorrow,”‘ April resumes. ‘A 35-year-old who is mature and wants a deep spiritual experience but can fuck like an 18-year-old? That’s a pretty good thing.’

OK, but what about women who don’t share April’s natural attraction to underweight men? Women like my girlfriend, for instance, who was happy enough to see the first 10 pounds drop off my calorie-restricted frame but likes the shape I’m in less and less as my weight keeps dropping?

‘You might have to change girlfriends,’ Paul quips. ‘Men are stereotyped and still associated with Arnold Schwarzenegger,’ he complains. ‘But when I see a man like Michael, I think that’s how a man should be: slim, bright, calorie-restricted!’

All eyes fall on Michael, and, for the first time, I get a good look at his hands. And though I’m sure the light must be playing tricks, I can’t help thinking those hands are actually a vivid shade of…

‘I know, isn’t it pretty?’ asks April. ‘I love the orange. I call him the Orange One.’

Michael smiles. ‘I consume an enormous amount of carotenoids – beta-carotene and lycopene – which are found in foods like carrots, kale, tomatoes. If I had skin like yours, the effect probably would be barely noticeable, but because my skin is an extremely pasty white to begin with…’

‘So wait,’ Adam interjects, ‘you eat so much kale, tomatoes, and carrots that your hands turn orange?’

‘Yes, isn’t it pretty?’ April asks again.

At which point Michael, having finished his helping of asparagus and Quorn, picks up his plate and does what any normal person who has not eaten a filling meal in years would do. He holds the plate up to his face and licks it clean.

For dessert, we get a CR-perfect parfait: organic strawberries, non-fat ricotta, flaxseed oil, and hazelnuts. It’s good, and gone too fast, and as long as we’re rewriting the book on table manners , I can’t see the harm in scooping out the last bits of ricotta with my fingers. April sees me and frowns. ‘You need to eat more. Right now,’ she says, bringing me seconds.

‘Kurzweil thinks we will reach actuarial escape velocity pretty soon,’ says Don. ‘What do you think, Michael?’

Michael pauses to collect his thoughts, and while he does, let’s fill in a blank or two. Ray Kurzweil is a best-selling futurist, given to flamboyant but well-researched predictions about the ‘transhumanist’ century ahead of us, in which artificial intelligence, intricate nanorobotry and other techno-marvels combine to reinvent humanity in the image of the machine. In the midst of it all is the concept of ‘actuarial escape velocity,’ a transhumanist term for that moment in the acceleration of biomedical progress when, for every year you live, technology adds another year or more to your life span. It’s a tipping point that, theoretically at least, never stops tipping.

‘I would like to hope 50 to 100 years,’ says Michael, speaking carefully. ‘Fifty to 100 years,’ says Don. ‘That may be too late for me.’

After the dishes are cleared and Adam and I have waved goodbye to my calorie-restricted dinner guests, I walk into the kitchen, and turn to Adam, one eyebrow raised, for confirmation that a calorie-restricted life might be worth living.

‘So, whoa,’ says Adam. ‘I have got to say that that was probably the blandest-tasting meal I’ve had since, like, ever.’

I’m confused. ‘But you said…’

‘I was being nice.’ An awkward silence reigns until at last Adam puts his hand on my shoulder, looks me in the eye, and says, ‘Dude. It was bad.’

Late the next morning, I awaken hungry, walk into McDonald’s, and consume a quarter pounder with cheese and a 12-ounce chocolate triple-thick shake. At cocktail hour, I drink several Cuba Libres and eat cheese-laden canapés. For dinner, I stop in at Katz’s Delicatessen on Houston Street and ingest one half of a two-inch-thick pastrami on rye, half a corned-beef sandwich, several pickled tomatoes, and a cream soda, and only after eating a slab of chocolate-coated Häagen-Dazs ice cream at bedtime do I begin to feel the first pangs of queasiness. For the first time in 63 days, I end the day without the slightest idea how many calories I ate or the least desire to know.

You would think it would have taken more than a few unkind remarks about Quorn to cancel my date with a calorie-restricted destiny, and you would be right. I liked these people. But, in the end, I made my way home that night with the sense that I had just come closer than ever to falling down the black hole of cult membership.

I know: what was I thinking? But I’m your average midlife secular professional. Like the tail-end baby-boomer I am, I grow more intimate each day with the fear of mortality, and, lacking spiritual faith, I am susceptible to scientific promises of longer, healthier life. I won’t belabour the point: just take a good look around your neighbourhood, your place of work. Take a look in the mirror.

Yes, CR flies in the face of common sense, but it’s got scientific evidence on its side. Yes, it’s a little crazy, but the crazinesses it requires are only those endemic to our age. And yes, by any objective standard, the food is lousy, but believe me: starve yourself long enough and even a tofu-coffee-macadamia-nut-and-flaxseed smoothie becomes ambrosia.

So if you’ve read this far and still think you could never, ever, do what my five dinner guests do to themselves every day, don’t kid yourself. I’ve seen the future, and it’s hungry.

Diary of a calorie-restrictive dieter

Alice Hart-Davis tries to prolong her life – on 1,800 calories a day

First, a word about hunger. You know the urge to grab a biscuit or some chocolate an hour after lunch? That is not hunger. Nor is the lurch in the stomach mid-morning after a light breakfast. Nor even the virtuously hollow feeling when you retire to bed rather empty because supper was at 6pm. The hunger I have come to know is a fierce, hard sensation that takes such a grip of your insides that when you try to hold your stomach in, it hurts. And after a few days of Calorie Restriction, it can kick in quite badly.

I know that hunger isn’t really what Calorie- Restriction (CR) is about but at first, it was overwhelming. My preparations before starting the regime amounted to mainlining the tin of Cadbury’s Heroes left over from Hallowe’en while reading up on CR on the web, joining the Calorie Restriction society and downloading their diet-monitoring software. I was going to work out my requirements very precisely, the number of grams of protein and carbs and all that, but for the next two days I was so beset by deadlines, children and so on that I was too busy to focus on it. So I just ate much less than usual and was soon very, very hungry. The idea behind calorie restriction is that you cut back your calorie intake signifi cantly (by anything from 10 to 60 per cent, depending on how hardcore you want to be) while maintaining excellent nutrition, in order to avoid the eff ects of ageing-related diseases and, indeed, ageing itself.

But the silly thing is that I have very little idea of (a) how many calories I eat in a day and (b) how many I need and therefore (c) by how much I should be cutting back. Could it be 2,000? Or more? That seems a lot for someone with a desk job, but then I cycle to get around, go to the gym, do yoga and play basketball, too. Calorie-counting fell out of fashion long ago. Since then, I’ve learned to count other things: grams of fi bre, fat, protein, carbs, not least because, as a health-and-beauty writer, I’m constantly trying out one diet or another in the interests of research.

The rest of the time, I try to eat sensibly, and reckon that a lite version of my Good Example to the Children regime will do, so on the fi rst day I eat: one boiled egg with half a piece of toast for breakfast; a large baked apple with 20g blueberries and 100g cottage cheese midmorning, 85g tinned tuna, 50g raw carrots and three Ryvitas for a late lunch, lots of cups of tea (which means 250ml of low-fat milk) and 100g of the fi lling of the chicken pie the children had for tea, with 200g broccoli for supper. The second day is much the same and, by the third morning, I’ve dropped two pounds. Feeling exhausted and hyperactive from being continuously half-empty, I finally get my head round Dr Walford’s Interactive Diet Planner, and CR begins to make sense.

As I painstakingly log each morsel of food, this brilliant bit of kit tots up precisely how many calories, grams of protein, carb and fat it amounts to, along with how many micrograms of minerals, vitamins and trace elements, and keeps a running total. I’ve plumped for a daily total of 1,600 calories, 40 per cent to come from carbs, 30 per cent each from fat and protein. I soon see that not only have I eaten far too little (that first day was 1,136 calories) in the past two days, but too little protein and monounsaturated fats. Plain fish with a dash of olive oil for elevenses evens up the balance and I start to feel more in control. It’s daunting, though, especially if, like me, a large part of your food intake comes from grazing ; noting down every surreptitious mouthful of chocolate peanuts soon adds up. Every Starbucks grande cappuccino is 143 calories (8.3g protein, 7.7g fat), while one 30g corner of my heavy home-made bread with peanut butter, nicked off the children at breakfast, appears to warrant 95 calories. Since CR is all about getting optimum nutrition with the fewest possible calories, anything with empty calories is clearly off the menu.

Luckily, I’m no foodie and hunger lowers my standards further. By day four I find that even plain, unflavoured, cold tofu tastes just fine when I’m ravenous, as does the cold vegetable soup which I can’t wait to heat up. Reading up on CR, it soon becomes apparent that its devotees are alarmingly hardcore; the sort of people who can happily get through the day on a few cups of green tea and a smoothie, then ‘feast’ on vegetables in the evening. Or they skip lunch and ’embrace’ the hunger that inevitably strikes mid-afternoon as part of their grand design to live longer and more healthily.

Week two

The scary thing is, by the end of the fi rst week, I begin to see what they mean. I’ve lost 4lb which means I’m going through the 10-stone barrier to a place I haven’t been since I was a teenager. I rather like being a bit hungry; it makes me feel buzzy, but also focused and it takes me back. At (boarding) school, I was always hungry, routinely starving myself , imagining if only I could reach eight stone, my life would be different.

And, as at school, I fi nd my stamina is already beginning to suff er when I exercise. Since June, I have been working out with David Marshall, the self-styled ‘Bodydoctor’ . Although I’m not eating much less for breakfast than normal, after the fi rst few rounds of press-ups and bicep curls I can feel my strength evaporating, which is alarming. The CR people are equivocal about aerobic exercise. They do advise load-bearing and resistance work (weights) since CR can adversely aff ect bone density, but they maintain that CR alone gives better results for longevity than aerobic exercise and that too much exercise is counterproductive. Hmm.

CR is not sociable , but there is little socialising to be avoided. I eat supper with the children before going out for drinks, then opt for fi zzy water . My only lunch date is steered to Pret (the tuna salad, without the dressing, provides 24g of protein for 178 calories).

As the second week goes on, I allow myself another 200 calories a day since the books (The Longevity Diet by Brian Delaney and Lisa Walford, and Beyond the 120 Year Diet by Roy Walford, the CR pioneer and father of Lisa) say you shouldn’t lose more than a pound or two each week. Unlike anorexia, CR is not slow selfdestruction through starvation.

This is eminently do able: 1,800 calories means 75g porridge, 50g yoghurt and a large baked apple for breakfast, 100g cottage cheese, 100g carrots and 25g hummus mid-morning, 100g roasted tomatoes with 75g plain chicken and 100g plain tofu at lunch, 16g cashew nuts, two satsumas and 100g grapes as a snack, a GI Sense bar which appeared on my desk and off ered 12g of protein, so I scoff ed it, then 75g salmon with 75g carrots and 140g broccoli for supper.

After three weeks

I’ve lost another 3lb and have to admit that I’m beginning to look rather bony. One sharp-eyed mum at the school gates, who is a doctor, is making warning faces at me not to lose any more. ‘ Your face is going all gaunt,’ she says. Mr Bodydoctor is distinctly unimpressed, too. ‘The fact is,’ he booms as he scrabbles at my back for some fat to measure in his callipers, ‘with all this muscle on it, your body needs about 1,600 calories a day just to exist. Then there’s all the exercise you do. Each work out will get through 1,000 calories . Your fat percentage is already down to single figures .’ My brain is whirring with calculations (1,600 x 4, plus 2,600 x 3, divided by 7, minus 20 per cent. It still comes to about 1,800 calories a day) as he delivers his parting shot: ‘If your body doesn’t have the fuel it needs from food, it cannibalises itself,’ he roars.

The trouble is, I’m rather loving it. Jeans are now comfortably roomy and being thinner makes me feel in control, and hence, clever and strong and superior, which I am old enough to know is very silly indeed. And if I carry on with CR, I’d be doing it for all the wrong reasons, like, just to see if I could ever be nine stone again. I don’t want to live to 120, particularly not if it means existing in a furious tizz of restraint and denial while all my friends enjoy themselves then drop dead around me. Besides, the chances of being run over by a bus, or indeed being blown up in a bus, remain the same . So I’ll only do it for another two weeks and give up for Christmas. Promise.