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We discover the benefits of intermittent fasting

Even though humans have been fasting in some form or another for thousands of years (we do it every night while we sleep!), the very idea has become controversial. We are taught to graze on small meals throughout the day and to keep snacks on hand ‘to keep our blood sugar steady’. We’re warned against the hazards of skipping meals: ‘it will put your body into starvation mode’ and bring your metabolism to a grinding halt; you will become shaky and light-headed; and unable to focus or even function.

Research, however, shows that none of this is actually true. In fact, abstaining from eating for a certain period has been shown to have tremendous health benefits.

‘The most obvious benefits of fasting are that it helps with weight loss and type 2 diabetes,’ writes Dr Jason Fung in his book, The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting. ‘[But] there are many other benefits, including autophagy (a cellular cleansing process), lipolysis (fat-burning), anti-aging benefits, and neurological benefits. In other words, fasting can benefit your brain and help your body stay younger.’

The fridge and the freezer

To understand the benefits of fasting, you need to understand how the body burns energy. When you eat, your body produces two sources of fuel: glucose – until a certain threshold is reached – then fat, stored in the liver or in fat deposits in the body. Glucose is stored in the liver as glycogen and easily accessed by the body. Fat is harder to access, and the body can store indefinite amounts of it.

Think of it this way: glycogen is the fridge – you can move food in and out of it easily, but there’s not that much space. Fat, on the other hand, is the freezer in the basement – it’s harder to get to, but you can pile up stores in there for later use.

The body uses glycogen for energy almost exclusively until it runs out – which it rarely does,

When you fast, your insulin levels drop, and once your body has burnt through your glycogen stores, it starts to break down fat for energy.

because you replenish it every time you eat. Which means that the stored fat is never accessed or used for energy. Simply put, ‘if your glycogen “fridge” is full, you will not use any of your fat in the “freezer”,’ says Dr Fung.

The other factor that comes into play is insulin, the key hormone involved in the storage and use of food energy. Whenever you eat, your insulin spikes, and insulin inhibits lipolysis.

‘That’s a fancy way of saying that insulin stops fat burning,’ says Dr Fung.

When you fast, your insulin levels drop, and once your body has burnt through your glycogen stores, it starts to break down fat for energy. This is a perfectly natural process; your body is not burning muscle or ‘starving’ or struggling to cope.

Lower insulin levels also have other benefits, such as improved insulin sensitivity (high insulin resistance is the main problem behind type 2 diabetes, and it has been linked to several other ailments like heart disease, stroke, Alzheimer’s and high blood pressure) and a natural boost in human growth hormone (HGH) secretion, which has anti-ageing benefits.

Fasting also provides the greatest known boost to autophagy: a form of cellular cleansing during which your body kills off and clears out old cells that aren’t functioning at their best any more. This function is unique to fasting because eating stops the self-cleaning process of autophagy dead in its tracks.

Fasting also provides the greatest known boost to autophagy: a form of cellular cleansing.

‘Hangry’

But what about hunger? We’re taught that hunger is something that builds until it becomes unbearable. Uncontrollable hunger is the number one worry when it comes to fasting, says Dr Fung.

‘Even some “experts” proclaim (incorrectly!) that [hunger] will leave you prone to overeating once the fast is over,’ he writes. ‘Most people worry that they’ll be unable to continue fasting because they will be overwhelmed with hunger.’

But research has shown that hunger actually diminishes with fasting. We’re conditioned to feel hunger at certain times, because (like Pavlov’s dog) we eat at regular intervals, and our bodies adapt to that schedule. But hunger actually has a natural circadian rhythm; it comes in waves.

‘It will build up, peak, then dissipate; all you have to do is ignore it,’ says Dr Fung. People who fast for longer periods consistently find that hunger is no longer a problem after two days. This is because ghrelin (the hunger hormone) peaks during the first two days of an extended fast, then steadily drops.