It’s the weight loss programme that everyone is talking about and it means you can eat whatever you want... most of the time. Mimi Spencer investigates.
“Oh, Meera’s doing that,” says my husband at the breakfast table, spooning Greek yoghurt onto a mountain of granola. I’ve just told him that I’m writing a piece about intermittent fasting (IF). My husband couldn’t be less interested in diets. Fitness? Definitely. Bikes? Absolutely. But not diets. And I’m surprised to discover that Meera is “doing” IF. She’s one of those no-nonsense women who you’d assume thinks dieting is for bimbos, narcissists and irredeemable fools. She is also built like a pencil. Why would she fast? “She told me all about it on the train to Exeter,” continues husband. “I think I might give it a go.”
“Giving it a go” involves an act of extreme, almost poetic simplicity: a dramatic calorie slash two days each week. That’s it. There’s no bible to follow, nothing to buy, no bars or shakes. For the moment, this is the Diet With No Name. Some call it intermittent fasting, others alternate day fasting (ADF) or the 5:2 – but they are all riffs on the same premise: twice a week, you eat little more than an egg, two satsumas, three oatcakes and a carrot.
The recent rush of interest in IF began after a Horizon programme called Eat, Fast, Live Longer was broadcast on BBC Two in August. Dr Michael Mosley followed the method for several months, losing 14lb and 25 per cent of his body fat in the process. Mosley’s conclusion was unequivocal: this was the “beginning of something huge... which could radically transform the nation’s health”. It was, he stated, “revolutionary”.
Watched by 2.5 million people, and by a quarter of a million more on YouTube, Mosley’s Horizon stressed the regime’s health-giving benefits – how, given base-level good health, a decent set of genes and careful supervision, it could substantially lower a catalogue of risk factors for cardiovascular disease, diabetes, stroke, several types of cancer, Alzheimer’s… In short, intermittent fasting could inhibit the ageing process.
Of course, what many viewers heard loudest was weight loss. Accelerated, straightforward, sustained weight loss. Sure, we’d all like to live longer – but that’s something for the future, like a pension pot. Weight loss is very much in the present tense, and all you have to do is fast. A bit. Not for ever, not daily, not even completely. This makes it, potentially at least, the biggest diet since Dukan, since Atkins: a novel way to lose weight which, as a bonus side dish, may help you to live longer, too.
Barely ten weeks on, and it seems that everybody is on it. When I mention it over coffee with the school-run mums, Liz says that Victoria has been doing it for weeks. Kathy, a paediatrician, started yesterday. It came up in Sasha’s office, and four of her colleagues were already doing it, all of them men. This is fascinating in itself, since, in my experience, men tend to approach diet fads the way they might approach a box of Lil-Lets. But IF is different. Men are early adopters on this one, possibly because it promises not just a leaner body, but a longer-lived, disease-resistant one; not just a flatter belly, but a sharper mind. It can’t hurt that Nasa is looking at fasting to improve the cognitive functioning of pilots. Perhaps Mosley is right. This could be huge.
“A lot of medics are embracing it,” he tells me, “because they see the hard evidence behind it. Until I started investigating fasting, like most doctors, I regarded it as a fringe activity – toxins being eliminated from the body and all that nonsense. But I was genuinely astonished by the research.”
So what exactly does the research reveal? Scientists have known since the Thirties that there is a link between restricted calorie intake and longevity – and we’ve all heard of the calorie restricters, the Californian “CRONies” (calorie restriction with optimal nutrition) who live like hunger strikers. But recent research by Professor Valter Longo at the Longevity Institute at the University of Southern California has revealed that occasional calorie restriction has a similar effect: you get the benefits without the purgatory.
When we consume calories, our cells are locked into what Mosley calls “go-go mode”; they burn fuel like fury and grow too fast for damage to be efficiently repaired. One of the agents that governs this process is insulin-like growth factor 1 (IGF-1), a hormone produced in the liver that keeps our cells constantly active. While we need adequate levels of IGF-1 when young and growing, high levels later in life accelerate the ageing process. When IGF-1 levels drop – as happens in a fast state – the body slows production of new cells and instead repairs old ones. This is “autophagy”, a word derived from the Greek for “self-eating”.
“The evidence comes from Laron mice that have been genetically engineered so they don’t respond to IGF-1,” explains Longo. “They are small but extraordinarily long-lived, typically surviving 40 per cent longer than average.” The oldest has lived to the human equivalent of 160 – and, vitally, they are immune to heart disease and cancer when they die. Immune to cancer. This is an astonishing discovery. Says Longo, “The results are so remarkable that we think oncologists should consider fasting as an option for patients who might have run out of alternatives.”
In the UK, a study led by research dietician Dr Michelle Harvie at the Genesis Prevention Centre in Manchester found that women on a restricted diet (650 calories, predominantly from milk, fruit and vegetables) for two days a week can lower their risk of breast cancer by up to 40 per cent. The key to weight loss, says Harvie, is compliance: “The two-day diet we devised could be a life-saver for women who find it difficult to restrict what they eat every day. There is a sensible message to come out of this: the standard approach is not based on evidence and it doesn’t work, so let’s try to be a bit more innovative. We’ve been studying intermittent fasting for seven years now and, as far as we know, this works.”
Before we put up the bunting, it’s worth noting that the science is still in its infancy; human trials are only just beginning. “What we don’t know yet,” says Harvie, “are the long-term effects. No one has yet done that work.”
What is increasingly widely accepted, though, is that short-term fasting can benefit the brain. “Dietary energy restriction extends life span and protects the brain against age-related disease,” confirms Mark Mattson, head of the laboratory of neurosciences at the National Institute on Ageing and professor of neuroscience at John Hopkins University in Baltimore. “When the brain goes under energy restriction, particularly when administered in intermittent bouts of major caloric restriction such as alternate day fasting, we see neural activity that’s associated with protection against degeneration from stroke and ageing.” A recent paper from researchers at the Scripps Research Institute in California established that “short-term fasting leads to a dramatic up-regulation in neuronal autophagy”.
“Ah, autophagy,” says Brad Pilon on the phone from Canada. “It’s just a beautiful, well-orchestrated, incredible thing.” If there’s a poster boy for intermittent fasting, it’s Pilon. At 5ft 10in, 12st 8lb and a mere 9 per cent body fat, he has been an IF evangelist for years. Armed with a masters in nutritional science from the University of Guelph, Ontario, he published Eat Stop Eat, outlining the method, in 2006. Nobody much noticed. The book just bumped along. “Everyone was grazing back then,” he recalls. “I was selling 20 books a month at most.” These days, he’s shifting 50 a day.
“Basically, fasting gives your body a chance to house-keep,” he says. “Constant growth is not a good thing. There must be time for recovery and rebuilding at a cellular level if optimal health is the goal.” Pilon boycotts all calories during his biweekly, 24-hour fasts; these typically run from 2pm to 2pm, leaving no single day completely deprived of food (and, says Pilon, “I get to sleep through most of the fast”). “Fat loss starts at about 12 hours into a fast,” he says, “and plateaus at around 18 hours.” At this point, the body is busying itself with autophagy. It is also in ketosis, a term you may recall if you have ever dabbled with Atkins – when the body has exhausted its glucose reserves and is tucking into fat.
“As fasting takes off,” he continues, “people are going to be interested in the metabolic stuff, but it’s the behavioural stuff that really matters. It’s about learning to eat less as a lifestyle. Sure, numbers are important, hormones, metabolic changes – but don’t get pulled into all that. We might find out that IGF-1 is not the big deal it’s made out to be. No matter what, the end result of fasting is better health. I’m commonly asked, ‘How many calories am I “allowed” during a fast? Can I go to that wedding if I’m fasting?’ For me, that’s not the point. The idea is to learn to take a total break from eating.” Michelle Harvie makes a similar point: “If anything, intermittent fasting helps people to recheck their diet. They think about what they eat. It’s not rocket science.”
Maybe not. But how difficult is it to do? Rather than Pilon’s total calorie annihilation, I – like many IF beginners I meet – go for the cheat’s 5:2 version, which allows women 500 calories on two non-consecutive fast days each week (it’s 600 for men). On my first fast day, I weigh 9st 6lb (60kg) and my BMI is an OK 21.4; my body fat, though in the “normal” range, seems enormous: 30 per cent. That’s 2st 11lb of fat… I imagine it in jars, the way Dr Christian would illustrate it on Embarrassing Bodies, yellow like lemon curd. It’s enough to put me off breakfast. Which, it turns out, is just as well.
It’s immediately clear that 500 calories looks pitiful if you gather them together in one place: a mug of lentil soup, a plum, half a chicken breast, seven blueberrries and a breadstick. It looks like tea for a toddler. Once weighed, measured, counted and cut into “inch cubes”, everything looks tiny. Usual portions are way out; to nudge under 500 calories, you’re looking at a quarter of a small avocado, a 3oz steak (around a third of an average serving), eight almonds, a bowl of carrot soup. No cheeky glass of vino with your salmon salad, no crusts from the kids’ tea, no pavlova – which is a tragedy if you happen to have one in the fridge.
Instead, my husband and I share an apple for lunch. I eat my half slowly, in small bites, the way you might consume something very rich, such as Valrhona chocolate. I consider the apple core. I quite fancy it, but would it send me over my lunch limit? I’ve already had 30g of Bran Flakes for breakfast. (166 calories. When a cereal box says “a 30g serving”, measure it. Go on. Be amazed. It’s not enough to fill a child’s cupped hand.) And there’s chicken salad for supper – a no-skin, white-meat, one-slice chicken salad to book-end my day. There will be some sprouts, a radish and a cherry tomato, perhaps a handful of leaves, a shaving of raw cabbage. And no pavlova. Until tomorrow.
After a week of 5:2, it’s clear that this is categorically not fasting, at least not as we know it. Although you are limited to around a quarter of the recommended daily calorie intake, there is still food going in, still flavours to occupy the mouth, still mini meals to define a day. It’s do-able. And the effects are immediate. I lose 3lb in a week.
By week three, the novelty has worn off. We’re a bit tetchy when it comes to the apple-sharing. Pilon’s advice is to stay busy – “No one’s hungry in the first few seconds of a skydive,” he says in his breezy, 9 per cent fat way. Curiously, though, over the course of a day, I don’t feel particularly hungry. There are occasional spikes, when I want to gnaw my shoes for sustenance. But for the most part, the hunger is a mere background hum, easy to ignore, like a tumble dryer in the room next door. Besides – and this, I think, is key – there’s no need to panic. The following day, just hours away, you can feed. This is what marks the 5:2 out from other restrictive regimes; if today is tough, tomorrow will always be infinitely sweeter.
And, though it may seem counter-intuitive, you really can eat whatever you please on the “off-duty” days, as demonstrated by Dr Krista Varady of the University of Illinois, one of the leading researchers in the field of alternate day fasting, who carried out a trial comparing two groups of overweight patients. One group was put on a low-fat diet on their feed days, while the other ate lasagne, pizza, fries – a typical American high-fat diet. “When they signed up for the study,” says Varady, “the people randomised into the high-fat group weren’t happy, because they assumed that they wouldn’t lose as much weight as those on the low-fat diet. But they did. They were losing as much and sometimes more weight, week after week.” According to Varady, most people don’t compensate for fasting by grossly overeating the next day. A calorie slash of 75 per cent on a fast day generally gives rise to a 15 per cent increase on the following feed day (as she might say, “Do the math”).
Three weeks in, and I’ve lost 5lb 8oz. My BMI is a sparky 20.4, and my body fat 23 per cent. I’ve had to buy new jeans. And new bras. I’m not sure how my brain is faring, but I knocked off the crossword this morning while the kettle boiled; Michael Mosley says he’s thrashing Su Doku. “I did a series of tests recently, and my cognitive performance had, in fact, improved,” he adds with a laugh.
So is this all too good to be true? As Michelle Harvie admits, we don’t yet know. Nutritionists are quick to point out the dangers of calorie restriction in any form for diabetics, anorexics, pregnant women, children and people who are already extremely lean. According to Mike Gibney, Professor of Food and Health at University College Dublin, “Such is the wealth of data on these diverse species that one must accept the literature that caloric restriction prolongs life expectancy. The big question is the translation of that concept to man.” Besides, as longevity expert Professor Steven Austad of the University of Texas puts it, we have yet to discover whether calorie restriction, if it works at all, “is anything more than the elimination of excess fat”.
All of this is food for thought, and for further research. Until then, occasional fasters should certainly proceed with care. There may be headaches, dizziness, fatigue, dehydration. Over in Southern California, Valter Longo himself advises caution: “There’s going to be a drop in blood pressure, a drop in glucose levels, and metabolic reprogramming,” he says. “Some people faint. It’s not common, but it happens.”
I haven’t fainted yet, but I do think I have gone far enough, so I’ve scaled back my fasting to one day a week. Michael Mosley has done the same. “I’ve plateaued a bit,” he tells me. “I’m 12st now and my wife said I was looking gaunt, so I decided to do the maintenance version of one day a week, to give my body a rest.” And does he still believe that intermittent fasting is a radical game-changer, a revolution for the world at large? “Only time will tell if this is a fad or something more meaningful,” he says. Right now, the jury’s out. But smaller jeans? Who’s going to argue with that?