How To Do Intermittent Fasting

14th April 2022

How To Do Intermittent Fasting

What is Intermittent Fasting?

Intermittent fasting consists of following an eating pattern where you either refrain from consuming calories in any form daily for a period of hours, or significantly reduce your calorie intake across your day. How you do intermittent fasting depends on the method you feel is right for you. 

The most common methods of intermittent fasting include:

TRE (time-restricted eating)

A popular form of fasting which is considered easy to follow and is encouraged while following any of the approaches on The Fast 800. This method involves reducing the hours in which you consume calories (your eating window) and not consuming calories in any form outside of that (your fasting window). Many people choose to take their fasting window overnight while they sleep and break their fast later in the morning, or finish their evening meal earlier. Often you’ll see TRE expressed as “fasting window:eating window”. For example, 12:12 may mean you consume calories anywhere within a window of 12 hours, like 8am-8pm, and fast for 12 hours between 8pm-8am. Some people may choose to extend their fasting window even further, however, we recommend fasting a maximum of 16 hours to be sustainable long-term (expressed as 16:8, which, for example, may be eating between 12-8pm).

5:2 fasting 

The 5:2 method of intermittent fasting, made popular by Dr Michael Mosley, places emphasis on reducing calories on two days of the week. While it’s evolved over the years, The New 5:2 involves two “fasting” days per week, where you consume about 800 calories of healthy and nutritious Mediterranean-style food and eat sensible portions of similar food with no caloric restriction for the remaining five days.

Alternate day fasting 

This involves switching between eating with no calorie restriction on one day, to consuming zero calories the next. On The Fast 800, we do not encourage this method for two reasons: there’s no significant benefit to fasting for longer than 16 hours, and consuming no calories at all for up to or beyond 36 hours is incredibly challenging for most people.

Benefits of intermittent fasting

Fasting is not a new concept and has been practised for hundreds of years in cultures across the globe. However, it has become significantly more popular in recent years due to an impressive amount of scientifically-proven benefits. 

There is mounting evidence that intermittent fasting may lead to:

    • improved insulin response, reducing type 2 diabetes risk;
    • better quality of sleep;
    • reduction in inflammatory arthritis;
    • maintenance of muscle mass with weight loss; and,
    • reduced risk of brain disease, such as Parkinson’s and dementia.

How to implement intermittent fasting

If you’re brand new to fasting and want to improve your metabolic health and lose weight, we recommend starting with either The New 5:2, TRE or a combination of both. 

When following The New 5:2, your fasting days are likely to need the most planning to ensure you’re getting the nutrients your body needs,  while limiting your calorie intake. Our Online Programme has meal plans available for you to take the planning away however, we always advise you eat between 50-70g protein on 800 calorie days. Here’s an example of what a fasting day might look like:


Intermittent Fasting Day 800 calories


When starting with TRE, it’s important to take it slow and begin with 12:12 – you may even find that you already do this naturally. Over time, as your body becomes familiar with fasting, you may want to gradually extend your fasting period by an hour or two each day until you reach 14:10 or 16:8. When extending a fasting window to follow a 14:10 or 16:8 pattern, some people prefer to eat two meals a day, rather than three; however, there is no scientific evidence that places one above the other so your method should be determined around what works best for you and your lifestyle. 

What to eat and drink during your fasting windows on TRE 

In periods of no calorie intake, like TRE fasting windows, there are still a few things you can enjoy without worrying about breaking your fast. 

  • Water – staying hydrated while fasting is incredibly important. We get around 20 per cent of our fluids from food and if you’re limiting your calorie intake, you need to compensate for this reduction. Additionally, if you’re opting to exercise, or simply increase your activity, alongside your fasting regime, you’ll need to consider how much you sweat (more so if you have a higher starting weight) and increase your water intake to stay effectively hydrated.
    Tip: Add lemon, lime or ginger to your water if you want to add a little more flavour.
  • Black coffee and tea For fasting, black tea and coffee are great as they have virtually no calories. If you are a coffee lover, be mindful of your caffeine intake – we recommend no more than two cups of coffee a day.
  • Sparkling water – Carbonated water is a good option if you want to mix up your drinks. The bubbles can often make you feel full and keep you away from the snack cupboard.

Drinks to avoid 

  • Diet drinks – Although they have zero calories, they certainly do not have zero ingredients. They maintain your sweet tooth and keep you craving the sugary stuff!

FAQ: Can I have a dash of milk in my tea? 

If you’re following Time Restricted Eating (TRE) and you’re unsure if you can manage without your morning cup of tea or coffee with milk, you can have one cup outside of your eating window with a dash of full fat milk (less than 30ml, which is around 20 calories) without it being detrimental. 

If you’re following any of the approaches that have fasting (800 calorie) days, like The Very Fast 800, The Fast 800 Keto or The New 5:2, it’s important to take the calories of your milk into consideration if you’re having multiple cups of tea or coffee throughout the day.

Also, for those wondering – toothpaste will certainly not break your fast so please don’t worry about brushing your teeth in the morning!

What to eat and drink during your eating windows

Here at The Fast 800, we highly encourage you to avoid snacking and instead enjoy filling and nutritious meals that will see you through and keep you satiated until your next sitting. 

Although snacking is intended to suppress hunger and fill any gaps, it actually does the opposite. 

Every time we eat, the carbohydrates in foods are broken down into sugars, which are intended to be used as energy. Each time this happens, our bodies respond by releasing insulin, which helps us use the glucose as fuel. 

However, the more this happens, the more we become resistant to insulin, and the less effective insulin becomes at retrieving and using glucose. This leaves excess glucose in the body, which prompts the body to hang on to existing fat, and store more, as energy reserves for the future. Without being able to use glucose as an immediate source of energy, we become tired, hungry and the desire to snack is raised again. It really is quite a vicious cycle. 

How can you help manage this?

By reducing your snacking habits. While it may be tricky at first, you’ll soon find a routine that means you won’t feel hungry between meals. Another way is to make sure you’re eating foods low in simple carbohydrates and high in protein and quality fats. Some of our Health Coaches on The Fast 800 have been experimenting with different food groups and their impact on blood sugars. You’ll see from the following graph that a high-in-carb breakfast can spike blood sugars dramatically, leaving a quicker drop and therefore increased hunger levels. Alternatively, a breakfast combining fats and protein had a more steady curve and was able to satisfy, despite being slightly higher in calories.


When I ate the diet cereal, I was immediately struck by how small the portion was. It definitely didn’t look big enough and if I’d been pouring it from a larger box, I would have had more! I ate it really quickly and immediately knew I wasn’t satisfied. If I hadn’t been undertaking this experiment I would have headed straight back to the kitchen to find more food. As it drew closer to lunch, I became more and more aware of my hunger, and I felt terrible! I found myself willing the clock to move faster so I could escape and have my lunch.”

– Nia, Health Coach

During eating windows, a Mediterranean-style diet is recommended. It is satisfying, delicious and has time and time again been recognised to be the healthiest diet in the world. Try some of these recipes, developed by our in-house nutritionist, or sign up to the Online Programme for over 550 more.

How The Fast 800 can offer support

We have seen huge success from our tens of thousands of members who have successfully, and sustainably, integrated intermittent fasting into their daily routine. 

Our Online Programme offers a flexible approach including intermittent fasting methods, depending on your health goals. The Fast 800 rapid weight loss approaches can help individuals who are currently obese or overweight lose weight quickly and maintain a healthy weight, using intermittent fasting practices. However, if you don’t have much weight to lose, we recommend starting on The New 5:2 approach or The Way of Life approach, with TRE alongside for the added benefits. 

The Online Programme provides daily meal plans for whichever approach is most suited to you, with options for three meals a day, or two meals a day for those wanting to extend their TRE to the 16:8 method. There is also a dedicated group for TRE and Fasting in our member-only social media-style platform, Community, for people looking to interact with like-minded members, with similar goals, and our expert Health Coaches.

“This is the only thing that ever worked for me. I’ve lost a stone and feel so much better. No more sugar spikes and crashes. No more headaches or feeling exhausted.”

Lisa, current member


References arrow down

Hatori, Vollmers et al (2012), Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet.

Gabel, Hoddy et al (2018), Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study

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