Michael Mosley has an aspiration many of us are likely to share. “I’d like to live a full and healthy life until I’m 80, then drop dead in an instant,” he declares.
It’s a laudable aim, one that is effectively the holy grail of human pursuits: most of us want to live a reasonably long time, but we also want to do so intact in both body and mind. Quite how we pull that off has been chewed over for centuries by everyone philosophers to scientists. Most are agreed on the basics: genetics, a healthy diet and exercise all play their part. But in a new Horizon documentary, Mosley, a qualified doctor who has become the face of popular science on the BBC, reveals compelling evidence about a surprising new key to healthy longevity.
However, there is no quick fix or pill-popping solution. Instead, the unpalatable (no pun intended) truth is that it could simply come down to cutting back on the amount we eat. For ever. “The bottom line is that calorie restriction is the only thing that’s ever really been shown to prolong life,” says Mosley.
This is not going to go down well in the heavy-bottomed West, where we can barely move without falling face-first into a snack. Then again, this isn’t the first time the 55-year-old trained medic and programme-maker has put the cat among the pigeons: earlier this year, he made a robust challenge to our gym culture by demonstrating that very small periods of intense exercise can be just as effective as sweating it out on the treadmill three times a week, picking up record viewing figures on the way.
“I wanted to take the premise of that programme further, and find out how science could help us stay fit and athletic for longer,” he says. A good starting point, he decided, would be a chat with Fauja Singh, a marathon runner who also happens to be 101 years old.
“What’s immediately striking about him is that he’s very skinny but very fit,” says Michael. “He’s 5ft 8in and weighs just over eight stone. He eats a calorie-light, vegetable and plant-based diet that still sustains him for his physical activity. What I took away from that is that eating relatively low amounts is a good thing.”
He’s not the first person to think this: across the globe there are a number of communities - among them Japan’s Okinawa population who follow a diet lower in calories and also have lifespans years longer than the global average. Meanwhile, experiments on a variety of species, among them fish, rodents and dogs, have shown that calorie restriction appears to increase both median and maximum lifespan.
Studies on whether it works in primates and its effects on human health are ongoing but, as Mosley explains, the thinking behind it makes sense: “Ultimately, ageing is a product of a high metabolic rate, which in turn increases the number of free radicals we consume. If you stress the body out by restricting calories or fasting, this seems to cause it to adapt and slow the metabolism down. It’s a version of what doesn’t kill you makes you stronger,” he says.
And so, in recent years, the calorie restriction movement has gathered momentum, in particular in - where else? - the United States, where Mosley travelled to meet one devotee. “For ten years he’s lived on 1,600 calories a day, almost a thousand less than the daily recommended requirement for adult males, and at 5ft 9in he weighs nine-and-a-half stone - he was originally 13 stone. He’s in great shape; he has a low bodyfat composition and his arteries are pristine. He was a compelling example of the way calorie restriction can improve overall health.”
Which is all very well for people with an iron discipline - but what about the rest of us? Most of us would struggle to pare down our intake so dramatically on a permanent basis. It turns out we may not need to, however: Mosley uncovered evidence that intermittent fasting may offer some of the benefits of ongoing calorie restriction. “I had a friend who used to fast and I’m afraid I rather dismissed it as hippy dippy rubbish, but actually it seems there’s something in it.”
The science centres around the presence of IGF-1, a hormone similar in molecular structure to insulin. It plays an important role in childhood growth and continues to have an anabolic effect in adults. It’s key to human development: low levels stunt growth, while high levels contribute to cancer and ageing. “Where fasting comes in is that studies suggest it can restrict the growth of IGF-1 in adults as long as you simultaneously cut the amount of protein you eat,” says Mosley.
It’s persuasive, but still a challenge to enact, as Mosley found when he fasted for three and a half days during the making of the programme. “It’s tough, but it does get easier,” he says. “There are flashpoints, but I found if you distract yourself the hunger pangs do disappear. I learnt that I can control my hunger.”
Nonetheless, aren’t we programmed to require three meals a day? “Of course not,” says Mosley. “Cavemen didn’t eat that way. A lot of it is cultural - everyone from your parents to your doctor tells you not to skip a meal, which means doing so kicks against our inherited wisdom. Some of it is about re-programming ourselves. What we think of as hunger is mainly habit.”
He points out that all the great religions, from Christianity to Judaism to Islam, encourage fasting. “The programme goes out during Ramadan, a period of intermittent fasting for Muslims. So I wonder if those religious elders were onto something.” Either way, he says, while he can’t guarantee that he will fast in the future, he has already incorporated some of what he has learnt into his lifestyle. “I have cut down on snacks and no longer graze all day long as I used to,” he confides. “It used to drive my wife mad, so if nothing else she is delighted.”
5 steps to longevity
1. Don’t eat 8pm- 8am Try stretching periods when you don’t eat. If you can manage it, even one day of fasting every two months is thought to have potential long-term health benefits.
2. Cut protein Reducing protein has been linked to increased longevity. You probably eat more than you think: the Government recommends 55 grams a day for adults between 19 and 50, but the average Brit scoffs 85 grams.
3. Drink more Fill up on fluids, in particular water and green tea - a good thing generally and particularly when fasting. The latter is full of antioxidants, which help to fight the nasty free radicals that are one of the principal causes of ageing.
4. Eat colourfully Follow as rich and varied a diet as possible: invoke the rainbow principle, and eat as many varied colours of food as possible.
5. Stop snacks Small gestures in the direction of fasting are also thought to have benefits.
Horizon: Eat, Fast and Live Longer is on tonight at 9pm on BBC2.