Every few months a new diet fad rolls into town; the Atkins diet, the cabbage soup diet, the baby food diet, the Hollywood diet. They may work for some, but there’s often concern about the long-term health of anyone sticking to them for long.
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Supporters of a new kind of diet claim it can do more than help with weight loss. Intermittent fasting, where the dieter severely restricts the food they eat on certain days, has been heralded by some as a miraculous scientific discovery.
Its fans claim it helps you lose weight, live longer, look younger and even ward off dementia.
Of course, fasting flies in the face of commonly-held beliefs – the NHS advises slimmers to never miss a meal. So how is it supposed to work?
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Here’s the theory. Our bodies have a growth hormone known as IGF-1, which helps us grow when we’re children. However, as adults it appears to cause aging, while high levels are linked to cancer, diabetes and other illnesses.
Fasting lowers your IGF-1 levels, which some scientists believe slows growth of new cells and prompts your body to repair its existing ones. It also encourages fat burning, so you lose weight.
Studies from the Baltimore National Institute on Aging suggest that fasting once or twice a week can protect the brain against illnesses including Alzheimer’s and Parkinson’s.
Experiments in mice and rats have shown fasting can increase their healthy lifespans by as much as 50 per cent. Some people think that humans could see similar benefits and there’s growing interest in fasting techniques.
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The 5:2 diet
One fasting regime has been particularly popular. It’s the 5:2 diet – two separate days of fasting a week. On those days, men can consume 600 calories and women just 500.
Dieters can choose to eat them all at once, or have several small meals throughout the day. It was made famous by the BBC’s Horizon programme Eat, Fast and Live Longer, in which the reporter tried a number of different fasting techniques.
He’s also written about his experience and the potential benefits.
We spoke to three people who’ve tried the 5:2 diet for themselves.
David, aged 32.
“I became interested in intermittent fasting because of suggestions that it helps you live longer and healthier. I’m not too fussed about losing weight as I wasn’t fat, although I’ve lost about 3kg in the four weeks I’ve been on the diet – my stomach is much leaner.
“Fast days are hard and I have to plan around them. I can’t go for a run or work out because I don’t always have the energy and I’m sometimes a bit short-tempered. I eat a small bowl of porridge for breakfast and then two small salads later in the day.
“But the payoff is good. I mean, I can eat pretty much what I want the rest of the week and potentially improve my long-term health.
“I certainly feel like this has been a lifestyle change rather than a fad diet, I think it’s something I’m going to commit to for a very long time.”
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Victoria, aged 61
“I’m a retired GP and I’ve always been quite sceptical of any kind of extreme diet. But after seeing a documentary about the potential health benefits, I decided to give it a go.
“My main motivation was to lose weight but I was also attracted by suggestions that it helps ward off Alzheimer’s. My mother suffered with dementia and I want to do all I can to reduce my risks of developing it.
“I’ve been trying it for five weeks now and I’ve lost about a pound a week.
“It’s a weird diet because it’s both really easy and really hard. On my fast days, I eat two very small meals, and I find it very hard sometimes not to give up and snack. But then, the rest of the week I can eat what I like – so I don’t feel guilty if I treat myself to a cake or have a biscuit. I think I’ll probably do this for the rest of my life.”
Stephanie, aged 30
“I really wanted to try intermittent fasting because I hate having to always think about my diet. I’ve had quite a lot of success with Slimming World, but you’re always working out whether you’re allowed something or not. With intermittent fasting, I’d only have to worry about my diet two days a week.
“However, I’ve decided not to do it. There have been no widespread studies in humans yet, so I researched it by reading online forums and blogs. There are suggestions that intermittent fasting damages fertility in women, and I haven’t finished growing my family just yet.
“Maybe I’ll come back to it in the future when I am done having babies - especially if there’s been a bit more research into the effects on humans rather than rats!”
Get your doctor on board
As one of our case studies pointed out, there have been no extensive trials into the potential benefit or harm of intermittent fasting for humans.
If you’re tempted to try it out, it’s sensible to talk to your doctor first to make sure doing so won’t put your health at risk.
But if the scientists are right and the benefits are so extreme, then your two fasts a week could become as important as your five a day.
Have you tried intermittent fasting? What do you eat on fast days? Is this just another fad diet or a new discovery? Share your experiences and thoughts with other readers in the comments below.