Intermittent Fasting and The Fast 800

We spoke to Dr Michael Mosley about The Fast 800, the benefits of intermittent fasting and how embracing a Mediterranean style diet could improve your health.

Written by The Fast 800
Middle Eastern Suhoor or Iftar meal

Medibank have partnered with The Fast 800 to share tips and advice for managing your health and wellbeing. The Fast 800 program is an innovative approach to weight management, using the latest scientific research to support a healthy lifestyle. Talk to your GP before starting any new health program.


Seven years ago, Dr Michael Mosley created the hugely popular 5:2 bringing intermittent fasting into the mainstream for the first time. Michael created this way of eating after discovering that he was a Type 2 diabetic. Instead of starting on medication he researched the benefits of intermittent fasting and cut his calories for two days a week, eating normally for the other five. He lost 9kg and his blood sugar returned to normal.

His new book, The Fast 800, embraces many of the same principles as the original 5:2 diet, encouraging intermittent fasting, a Mediterranean style diet and a three-stage approach to tailoring a regime that works for the individual. However, based on the latest science, the number of calories recommended whilst fasting has been upped to 800.

We spoke to Dr Michael Mosley about The Fast 800, the benefits of intermittent fasting and how embracing a Mediterranean style diet could improve your health.

Who is The Fast 800 for?

The core objectives of The Fast 800 are to help people lose weight and reduce their blood sugar levels as part of improving overall health.

“There are plenty of ways to improve your health and even practice intermittent fasting that are different to what is advocated in The Fast 800,” says Michael. “Different things suit different people. In general, this program is aimed at people who are at risk of Type 2 diabetes and are wanting to lose weight to better their health outcomes.”

As with any way of eating, The Fast 800 may not be suitable for everyone so make sure you check with your health professional before making any changes to your diet.

What is intermittent fasting and should we all be doing it?

For all its popularity, intermittent fasting is sometimes misunderstood. The word fasting can conjure images of starvation however the time restricted eating that Dr Mosley espouses is not about deprivation.

“There’s many different ways to practice intermittent fasting. There’s the intensive phase, The Very Fast 800, where you eat 800 calories every day, there’s The New 5:2 where you limit your calories to 800 for two days a week and then there’s also time restricted eating where you limit your food intake to a certain number of hours in the day,” says Michael.

"In one of the first human trials of time-restricted eating, carried out with the help of the University of Surrey, two groups of healthy volunteers ate the same food, but the group on a time-restricted eating plan (eating breakfast 90 minutes later than usual, and dinner 90 minutes earlier each day) replicated the mouse studies. They lost body fat and saw bigger falls in blood sugar levels and cholesterol than the control group."

 “There’s more and more evidence emerging to suggest that when you eat is important. There’s research by Dr. Satchin Panda, of the world-renowned Salk Institute in California, that shows that giving your body some daily down-time from the work of eating and digesting, you can unlock powerful repair pathways that protect against illness, ageing and obesity,” says Michael.

So how can we implement this into our daily lives? Michael suggests building up slowly.

“You could start by finishing eating for the day at 8pm and not starting again til 8am the following day. That’s a 12 hour fast (12:12). You could then build up to finishing eating at 7pm and not starting again until 9am for a 14 hour fast. Actually, a lot of people find that eating in a shorter window makes fasting days a lot easier, however it’s a good habit to get into on non- fast days too.”

Why 800 calories?

“Eating 800 calories a day has been shown to be particularly effective for weight loss because it’s high enough to sustain you, so that you don’t feel hungry and to allow you to get the nutrients you need as part of a healthy balanced diet whilst also being low enough to allow you to lose weight quickly and see other beneficial health changes,” says Michael.

“In studies of 800 calories done by Professor Roy Taylor at Newcastle University, participants, on average, sustained a 10 kilogram weight loss for a year. The results were so impressive that the British Health Service is going to roll out a program testing it on 5000 people.”

Low calorie diets have often been criticised as ‘crash dieting’ or associated with starvation and being unsustainable. However, The Fast 800 is a far cry from The Cabbage soup diet or others of its kind.

“The Fast 800 is based on cutting-edge medical research. And crucially, it works,” says Michael.

“It’s not about depriving yourself, it’s about embracing a new way of eating including the principles of time restricted eating and a Mediterranean diet rich in lean proteins, vegetables and healthy fats such as olive oil and nuts. The recipes are actually delicious, I think many people are surprised by how much they enjoy eating them.”

Indeed, in The Fast 800 what you eat is just as important as how much you eat. Michael advocates for the traditional Mediterranean style of eating (if you thought pizza and pasta were on the menu, think again) that involves moving away from processed foods and towards eating food cooked from scratch and rich in vegetables, fibre and healthy fats.

How long should you stay on The Fast 800?

If the prospect of eating 800 calories a day for the rest of your life feels somewhat daunting, fear not. The Fast 800 is designed to help you lose weight quickly and then transition to a more manageable way of eating.

“We recommend that you don’t go on the 800 calories a day eating plan for more than 12 weeks” Michael advises “once you’ve done that or if you’ve hit your target weight, we recommend that you transition to the 5:2 or The Way of Life plan outlined in The Fast 800 book and online program in order to maintain your results in a flexible and sustainable way.

The Fast 800 online program caters for this transition to a more flexible life by offering a three-stage approach. Once you’ve followed the 800 calories a day to kick start your weight loss, you are encouraged to transition to stage 2, Intermittent Fasting with the new 5:2. Then finally to stage 3, the maintenance stage, which encourages a lowish-carb Mediterranean style approach with no calorie counting that allows the occasional treat.

 “The great thing about the program is that it is designed to be something of a tool in your back pocket that you can revisit whenever you need to. Life gets in the way of healthy eating sometimes so if you’ve been on holiday or over indulged for a period, being able to return to The Fast 800 for a couple of weeks is a great way to keep your weight in a healthy range.”

How will I know if The Fast 800 is right for me?

Michael recommends trying it for two weeks and assessing how you feel and where you are at in terms of your weight loss goals.

“Yes, you have to make sure you’re getting all the necessary nutrients. It’s not suitable for everyone. My advice is to give it a go for two weeks. If you feel dreadful, stop. If you feel good, [persist]. I do recommend you don’t go on it for more than 10-12 weeks.”

Does rapid weight loss mean you’re less likely to keep it off in the long term?

There is a widespread belief that long term sustainable weight loss comes as a result of slow, steady losses over a number of weeks, months or even years. However, Michael disagrees with the idea that quick weight loss is unsustainable.

“We looked at numerous studies that have compared slow and steady weight loss with rapid and there is some evidence to show that you’d actually do better to lose weight quickly rather than slowly,” Michael says.

“In one particular study researchers took 200 obese volunteers and put half of them on a low calorie diet for 12 weeks.  The other half were asked to cut their calories by 500 a day, enough to lose around a pound a week. They were asked to do this for 36 weeks. What they found was that the drop out rate amongst the steady dieters was very high; less than half of them made it to the end of the 36 weeks. Most of them said they were frustrated at the slow progress. By comparison 80% of the rapid weight loss group stuck with it for the duration of the study.”

Although the study showed that both groups put some amount of weight back on in the three years following the 36-week period, the amount of weight gained was similar.

“Rapid weight loss encourages your body to switch over to fat burning. It also reduces insulin levels, increases growth hormone and boosts levels of a hormone called BDNF in the brain, which helps improve your mood,” says Michael.

What are the benefits of intermittent fasting?

“These days we have food readily available to us 24/7,” says Michael. “It’s not uncommon for us to graze throughout the day or eat between meals or late in the evening. The problem is the digestive process never stops, except for briefly whilst we sleep and your body has to work continually to process all the nutrients and toxins in your food. It doesn’t get a break. Cutting back on the amount you eat or the window in which you eat can give your body a chance to rest it’s freed up to begin that process of repair.”

Crucially, intermittent fasting is not a crash diet or a way to lose weight for external appearance. It is about improving our health and the benefits are far reaching and, in some cases, surprising.

IF has been linked to reducing our risk of type 2 diabetes, boosting your brain power, reducing risk of some cancers, improving our mood, aiding better sleep, bolstering our immune system and increasing heart health. 

“One of the most surprising benefits I found was that I no longer snore,” says Michael. “Although really it’s not all that surprising because the uncomfortable truth is the reason most of us snore is because we’re overweight. When I put myself on the 5:2 diet, back in 2012, and lost 20lb (9kg), I also lost an inch of fat around my neck, and the snoring stopped completely.”

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Written by The Fast 800

The Fast 800 is an innovative approach to healthy living and weight loss based on the latest scientific research.

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