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What's the big deal about intermittent fasting?

You already know that what you eat is very important for your health and wellbeing. But not eating is just as important! Extended periods of not eating are called ‘intermittent fasting’ and when the body fasts, all kinds of magic can happen, from accelerated weight loss (and specifically fat loss) to normalising of your blood sugar levels, cholesterol and blood pressure.

Your body gets the chance to rest and repair in a way that it can never do when you are constantly grazing on food. You will also save time and even money!

So what is intermittent fasting?

Fasting very simply means ‘not eating’, but it’s a lot different to ‘starving’ yourself. Fasting is an entirely natural process which your body does every night while you sleep and when you extend the period of fasting, the benefits are even greater.

There are many different ways you can fast, some of them easier and more practical than others. You can choose to fast overnight (called time restricted eating or intermittent fasting), alternate day fasting, long fasts or two days a week (typically called the 5:2). In this article we will cover the time restricted eating and 5:2 fasting.

Fasting is nothing new. Human beings have fasted for millennia without detrimental consequences to health. There were times when food was plentiful and there were times when food was scarce. Fasting has been somewhat forgotten until relatively recently yet it’s probably the oldest and most powerful dietary intervention with huge therapeutic potential.

When you eat, often you’re taking in more food (and energy) than you need at that time so the surplus is stored away for use later. The following diagram outlines how to body processes and stores energy:

The most basic difference between these two storage spaces is that one is limited but easily available (the energy stored in the liver) and the other is harder to get to, but there is an almost unlimited reserve (the energy stored in the fat cells). So, if eating involves the body making insulin and storing excess sugar as body fat, fasting results in the process working in reverse. Not eating means insulin drops and the body has to start using the stored energy so your body switches to burning your body fat instead.

When eating and fasting are balanced you maintain a stable weight. But when you are eating and grazing constantly throughout the day, you are supplying your body with too much ‘energy’ and can start to put on weight because you are not giving your body any opportunity to use up the stored food energy.

To get your body back into balance and to lose weight you need to burn the energy you have in storage by fasting.

The benefits of fasting

The most obvious benefit of fasting is weight loss, but there are many other positive benefits reported by those who fast regularly. These include:

  • More energy

  • Improved concentration and feeling more alert

  • Lowered cholesterol

  • Reduction in inflammation

  • Better stress management

  • Better digestion

  • Better immunity

  • Slower ageing

  • Improved brain function and lower risk of dementia.

Different types of fasting

Time Restricted Eating

Probably the fast most recommended by nutrition practitioners is Time Restricted Eating (TRE) and it involves quite literally restricting the hours in which you eat.

12-hour fast

Eat breakfast at 7am and dinner at 7pm balanced by 12 hours fasting. This is how we all used to eat, 3 meals a day with no snacks in between. You would do this on a daily basis.

Extending the fast to 14 hours (with an eating window of 10 hours) or better still 16 hours (with an eating window of 8 hours) brings increased benefits. That would mean having breakfast at 9am (14-hour fast) or 11am (16-hour fast), then having your last meal at 7pm. A 16-hour fast is sometimes referred to as the ‘lean gains method’. You would do this on a daily (or almost daily) basis, adjusting the time you eat your breakfast (or even skipping breakfast entirely) depending on the timing of the evening meal the night before.

5:2 Fasting

The 5:2 diet, made popular by Dr Michael Mosley, involves eating normally for 5 days during the week and ‘fasting’ for two non-consecutive days. Strictly, these are not actually fast days, because you are allowed to eat, but you restrict your calories to 600 (for men) and 500 (for women) a day. In his latest book “The Fast 800”, Mosley opts for 800 calories a day, which is high enough to be manageable, while low enough to bring in some metabolic changes. In "The Fast 800" he also suggests readers combine the low calorie days with time restricted eating.

Who shouldn’t fast?

Fasting may not work for everyone. If you are diabetic or very stressed, it is important to get your blood sugar levels on to an even keel first and TRE is not recommended. Start with a 12-hour fast on just two non-consecutive days per week to see how you get on. If you have thyroid issues, speak to your nutrition practitioner before trying fasting.

It’s not appropriate for children, pregnant women or breast feeding women, anyone very underweight (BMI less than 18) or those recovering from eating disorders.

Getting started with fasting

The first job is to choose the kind of fast you are going to do and stick to it. If you know you’ve been eating a diet that’s not great, you’re a big snacker or you eat late at night, starting with a 12-hour fast is what you need at first. Do this every day for a week, eating three meals a day and no snacks.

As this starts to feel manageable (or if you are already pretty much eating to this kind of pattern), stretch your fast to 14 or 16 hours, again eating meals but no snacks in between.

Whichever of these two options you choose, the ideal scenario is that you work alongside a nutrition professional who can design a food plan that will feed and nurture your body with the right foods during your ‘eating window’, so you can get the maximum health benefits.

They will also be able to tailor a programme so that it tackles any other health goals that you have. Longer fasts (which I haven’t gone into here) are trickier to follow and should be carried out only when working with a nutrition professional.

What you can consume when fasting


You must stay hydrated and drink plenty of water. You can flavour the water with lemon, ginger, mint or cucumber but avoid artificial flavours or sugar free cordial.


Any kind of tea is fine: black tea, green tea or herbal teas. Ideally without milk.


Coffee is fine when you are fasting. Black coffee is ideal

Tips for Fasting

Keep Busy

Keeping busy takes your mind off the fasting process and limits your internal questioning. Often people who are new to fasting will be looking for something to be wrong, ‘will I start feeling hungry soon?’ and so on. Try to do all your usual activities exactly as you would normally do. It can take your body a little time to adjust to your new fasting regime.

Ride out the hunger

Until you become an experienced faster, there may be times when you feel hungry. Rest assured, your body has all it needs in terms of nutrition (your stored fat) to power you through the day. Hunger is just a feeling. Sometimes it can be a powerful one. The reality is that hunger is like a wave that may come and go. Drinking a large glass of water or a mug of herbal tea when you feel the wave of hunger is a good tactic.

Tune in

If you hit a day when fasting really doesn’t seem like the right thing to do, then don’t do it. Some women feel that they may not feel like fasting in the few days leading up to their period for example.

What to eat when you break your fast

When you have been fasting, your insulin levels are very low and the body has been using the stored fat as energy. To continue to burn fat, the ideal scenario is that you eat a diet low in starchy carbohydrates, so that there is less sugar in the blood for the body to use and store. It will, therefore, naturally continue using the fat stores.

A diet low in starchy carbohydrates is called a low GL (or low glycaemic load diet) and is based on protein (like eggs, meat, poultry and, fish), unprocessed foods full of soluble fibre (like oats, beans and lentils), foods high in healthy fats (like oily fish, avocados, nuts and seeds) and plenty of vegetables (limiting starchy veg like potatoes and parsnips). There is an emphasis on choosing smaller amounts of rice, pasta, bread and pastries.

Common Myths about Fasting

It’s important to have breakfast everyday

No, it’s not. Skipping the first meal of the day just gives your body more time to burn stored energy. As you start to get hungry later in the morning, make sure you have something healthy to eat so you’re not forced to hunt out sugar snacks and undo the good work.

Fasting is the same as cutting calories

Not true. Cutting calories is reducing the amount you eat or at least the energy you take in from food. Most shorter fasts simply ask that you consume your calories within a shorter period of time.

Fasting puts you in ‘starvation mode’ and slows down your metabolism

Again this is not true. Studies show that repeated low calorie diets can lead to a reduction in the resting metabolic rate (what we often refer to as ‘metabolism’) where intermittent fasting does not.

Fasting makes you over-eat when you’reallowed to eat

Another myth. The more you get into regular fasting, the less hungry you feel. The body has plenty of extra nutrients to use (i.e. your fat stores).

Fasting makes you lose muscle

Humans never would have survived periods of fasting if the body started to burn muscle instead of fat for energy, just because they couldn’t eat every 4 hours. The body stores energy as fat and uses this instead of muscle when sugar levels are very low. Studies into alternate day fasting for example show that fat mass decreases rather than muscle. The breakdown of muscle typically only occurs when body fat drops to around 4% – and this is very, very low, so really there’s nothing to worry about.


Intermittent Fasting has become a popular method for weight loss. It's easy to incorporate into modern lifestyles and doesn’t require calorie counting or following a complicated formula. I have learned that TRE works well for me and I’m able to easily adjust my eating window in response to whatever’s happening in my life on a day-to-day basis.

Let me know, have you tried any of these forms of intermittent fasting? What has been your experience, your struggles?

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