What is Intermittent Fasting? – According To Science


Welcome to “According to Science.” I’m Zoe Foulkes. Did you skip breakfast today? Did you also skip lunch? Are you Jimmy Kimmel? If you answered ‘yes’ to all three questions, and yes, statistically, that’s very unlikely, you’re practicing something called intermittent fasting, the trendy eating method that the late night talk show
host credits for recently helping him lose 25 pounds. So what exactly is intermittent fasting? Fasting itself has been around almost as long
as humans have been around. Hippocrates and Plato were fans of fasting. And most major religions have rituals that
involve the practice. But using fasting to lose weight or for other
health benefits is relatively new and has attracted more modern philosophers like Hugh Jackman, Nicole Kidman and Benedict Cumberbatch. And while there are many ways to go about fasting, most of them fall into one of three methods. The first: alternate day fasting, where every other day you eat a small 500-calorie meal. The second: the 5:2 diet, in which you eat normally for five days and then eat a 500-calorie meal on your two fasting days. Third: the time-restricted diet, in which you eat as you normally would, but you cram it into six or eight-hour window of time. So why is fasting different than eating
less throughout the day? When we eat, we create more energy than we
can use. This excess energy gets stored for later use. And there are two places to store this energy. First, there’s the liver, where the energy is stored as glycogen. The problem is, there’s not a lot of storage
in the liver. So when it’s full, the liver turns
the excess into fat, which can be exported all over the body, which has unlimited storage space. But it takes about ten to twelve hours for the
energy stored in the liver to be used up. So when we fast for longer than that, this
lowers our level of insulin, the hormone that helps store energy, and this tells the body to begin to use
the energy it’s stored as fat. The benefits may go beyond weight loss. When the body switches to using fat stores for energy, it produces compounds called ketones, which have been found to have benefits
for our brain health. One theory is that intermittent fasting is
beneficial, because fasting produces a mild form of stress that activates our cellular
immune system to release protective proteins. So the real question: should we try it? The answer, like so many things involving
Benedict Cumberbatch, is complicated. First of all, most of the studies showing
benefits of intermittent fasting were done on mice. There have been a few studies on humans, however, some of which showed that intermittent fasting can be more effective for weight loss than
simple low-calorie diets. Another showed reduced cardiovascular risk. So if you have a mouse, and he or she is having
weight problems, sure, give it a try. The problem for the rest of us is that it’s
difficult. Although it’s actually closer to how
our ancestors ate, there weren’t a lot of snacks around in the hunter-gatherer times, it’s hard in the age of plenty. And it should definitely not be tried by pregnant women, children, the elderly, those with diabetes and those on medicine. If you’re going to try it, experts advise that
you go slow, warning that the first week or two might involve headaches, tiredness and grouchiness. So for the brave ones, happy not eating!

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Reader Comments

  1. Travis Statham

    A couple of corrections. There's a 4th way to do IF – you eat a ketogenic diet of less than 20 grams of carbohydrates a day – which releases ketone bodies as your primary energy source. When you eat keto – you're naturally far less hungry because you're not activating insulin because you're not eating carbohydrates. Carbohydrates get stored as fat through de novo lipogenesis and glycogen – but if you don't eat any – your liver keeps producing ketone bodies and you have a consistent and efficient energy source that lasts through out the day/week. IF is best done when combined with keto – thus you wake up and you're not hungry for breakfast and you can fast until midday before having a lunch. Some even do OMAD – one meal a day – where they eat 2-3 pounds of fatty meat (vegetables are optional and actually unnecessary despite popular opinion). Because you're using ketone bodies as energy, and they come from Free fatty acids released by your adipose tissue – you can lose weight and you're not activating the storage mechanism of insulin.

    Keto + IF is the number one best way to lose weight, and it takes pretty much no effort to not eat breakfast. In fact, breakfast was originally invented by marketing executives to create a demand for cereal and milk.

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