Everything you need to know about the 16:8 intermittent fasting diet

Time-restricted eating is trending

Focus on fruit and veg, low-fat dairy, wholegrains, fish, poultry and nuts. Image: Pexels

The intermittent fasting plan which involves eating in an eight-hour window has garnered legions of fans including Jennifer Aniston - and for good reason. 

Crash diets don’t work. There, we said it. And we’re not sad about it, either, given there’s nothing safe, sustainable or, quite frankly, fun, about starving ourselves or obsessing over calories.

The good news? A growing number of research studies are backing one healthy plan that lets you eat your favourite foods, drink alcohol (in moderation, of course) and still lose excess kilos. No sign-up fees, no special meals, no potions or branded foods. The solution is surprisingly simple.

The magic lies in what scientists call “time-restricted eating” (TRE), better known as the 16:8 diet, which involves consuming all of your daily calories within an eight-hour window, leaving 16 hours without food. And there’s a reason it’s wildly popular – and not just for the weight-loss benefits. Think increased energy, a sharper mind and overall better health.

Like what you see? Sign up to our bodyandsoul.com.au newsletter for more stories like this.

During winter months, this method can be socially restrictive – after all, who wants to book a restaurant table for 4pm, or explain to a puzzled host they can’t eat after seven? But now, as the warmer days treat us to later sunsets and early aperitive hours, it’s the perfect time to give this science-backed approach a try. And there’s considerable evidence it works.

But first, a quick science lesson. During a 16-hour overnight mini fast, the body is forced to work harder to burn calories, giving metabolism and the energy centre of the body’s cells a chance to reset. In a review article published in The New England Journal of Medicine last year, Dr Mark Mattson, a neuroscientist at Johns Hopkins University School of Medicine, suggested the approach can improve health and reduce weight. It works partly because you consume fewer calories when you have only a narrow window in which to eat.

But researchers believe that even brief periods of fasting trigger a biological response to food scarcity called metabolic switching, meaning that once cells have used up their stores of sugar, they begin burning body fat instead.

Researchers believe when you eat is just as important as what you eat. Image: Pexels

In one study at the University of Illinois, 23 obese people switched to eating only between the hours of 10am and 6pm. During that eight-hour window they could consume any type or quantity of food, but had to commit to consuming only water or caloriefree drinks for the remainder of the day and night. Compared with a control group that followed a different type of fasting approach, the 16:8 dieters consumed 350 fewer calories a day than even the other fasters and lost three per cent more body weight after 12 weeks.

Sound good? Then read on for exactly how to get started and reap major health and wellbeing benefits.

1. Don't eat after 7pm

It’s important to get the timing of your meals right. Studies show the 16:8 plan is more effective when your eight-hour eating window starts earlier in the day, when the body is best at metabolising food. Go for the 10am to 6pm or 11am to 7pm slot, rather than one that starts after midday. Otherwise you end up having dinner later in the evening, when metabolism is sluggish. The good news is that the calorie distribution within the window doesn’t matter – you can have a big breakfast, or a big dinner, whichever is your preference.

Of course, it’s not an excuse to binge on camembert and Pringles within your eight-hour window. Mattson advises 16:8 dieters to “eat healthy foods, including wholegrains, healthy fats and protein, limit saturated fats and avoid sugar and refined carbohydrates.” But you do have a lot of flexibility.

Australian dietitian, Melissa Meier, says there’s credit to this kind of approach, as long as nutrition is still taken into consideration. “Just because you’re fasting doesn’t mean you can go hell for leather on whatever you want to eat during your eating window,” she stresses. “Focus on fruit and veg, low-fat dairy, wholegrains, fish, poultry and nuts – all super-healthy foods that can help you lose weight. Plus, it’ll help to lower your blood pressure, and can cut your risk of diabetes and heart disease.”

Dieters are advised to eat healthy foods, including wholegrains, healthy fats and protein. Image: iStock

2. Drop 500 calories with very little effort 

One of the main reasons TRE has so many ardent fans? It results in a 20 per cent daily calorie deficit, meaning that if you normally eat 2,500 calories a day, this would probably fall by 500 calories without a conscious effort to eat more healthily or add more exercise.

For most people, the result is that you would lose about a kilo a week. It’s also less arduous than other diets, partly because for much of the fasting period you’ll be asleep.

“One of the benefits of the 16:8 diet may be that it’s easier for people to maintain,” says Krista Varady, an associate professor of kinesiology and nutrition and the lead author of the Illinois paper. “Fewer participants dropped out of this study when compared to studies on other fasting diets.”

Mattson suggests starting with just a few days a week of the 16:8 approach rather than “going cold turkey”. Sudden restriction can leave you “feeling hungry and irritable”, although that usually passes quickly as the body and brain become accustomed to the new habit

3. Keep track of your alcohol intake 

Reality check: many of us are probably drinking too much, and with the best will in the world, it would take a strong person to cut out alcohol entirely, especially as school holidays and end-of-year celebrations start kicking off. But if you’re following the 16:8 approach and keen to see results, be sure to down any bevvies within your eating window – along with any other calorific drinks (water and black tea or coffee are fine).

The reason? “Alcohol leads to a loss of dietary self-control, and one drink can make us think food tastes better, so we want to eat more – bad news if you’re trying to lose weight,” says Dr Duane Mellor, a dietitian and senior teaching fellow at Aston University medical school. “It’s also highly calorific.”

The major contributor to the high-calorie count in alcohol is sugar, as it is one of the main ingredients involved in the chemical fermentation process. In fact, alcohol contributes more calories per gram than other ingredients in our favourite beers, wines and spirits.

According to the Australian alcohol guidelines for adults, daily drinkers should introduce regular days off the booze – preferably two consecutive alcohol-free days – which will also slash your calorie intake significantly. The key? Stick to small servings. A standard 175ml glass of wine contains about 160 calories, while a large glass (250ml) contains 225 calories.

And while it’s all too easy to fall into the habit of cracking a bottle of wine early into the evening, steering clear is the best way to curb unwanted kilos. When people were asked to drink red wine before and during a meal of garlic bread and pizza, they consumed 25 per cent more calories from the food than a control group who didn’t imbibe. “The effects of wine on appetite are immediate and stimulate food intake early in the meal,” said researchers at Glasgow Caledonian University. Duly noted.

Your best bet is to give the booze a break. Image: Pexels

4. Eat plenty of foods that contain vitamin A

Think oily fish, yoghurt and eggs. And not just because they’re packed with healthy macros. A study from Vienna is the latest to show that vitamin A can support healthy weight loss. Researchers have previously shown a deficiency of vitamin A is linked to weight gain, but it now seems that the reverse is also true. According to the researchers writing in the journal Molecular Metabolism, vitamin A helps to convert ‘bad’ white adipose tissue (the blobby fat we are trying to get rid of from our stomachs and thighs) into ‘good’ brown fat that is a potent calorie burner, a process known as ‘browning’. So throw eggs into omelettes and frittatas, add salmon to salads, pastas and bagels, or dollop yoghurt on everything from muesli to your morning bowl of berries to unlock major health and wellbeing benefits.

5. Get at least six hours of sleep and don't work late 

If you’re serious about dropping kilos and maintaining a healthy weight, don’t be tempted to work late or sit up binge-watching box sets. A single night of four hours’ sleep has been shown in a trial to impair the body’s ability to process glucose, which, says the author Emma Sweeney, a lecturer in exercise and health science at Nottingham Trent University, means excess glucose could be converted to fatty acids and stored as body fat.

Some researchers have shown that two weeks of getting too little sleep (about five and a half hours) at the same time as trying to lose weight results in people dropping less fat – and more lean tissue including muscle – when compared with dieters who get a solid eight and a half hours.

“It’s known that hunger hormones increase and satiety hormones decrease when we’re tired,” says Dr Nicola Barclay, a lecturer in sleep medicine at the Sleep and Circadian Neuroscience Institute at the University of Oxford, and an adviser to medical sleep-aid company, Mammoth. “We also crave more sugar and carbs due to the altered regulation of these hormones, which is why it’s linked to weight gain.”

A lack of sleep has been linked to weight gain. Image: Getty

6. Eat 30g of fibre a day 

It should go without saying, but make sure you include plenty of fruit, vegetables and pulses in your eating window. Few of us eat enough fibre, with most Aussies missing the ideal daily amount of 30g.

“Fibre plays a very important role in making us feel fuller and improving our gut health, both of which have an impact on weight,” says dietitian Helen Bond.

Up your intake of fibre-rich foods, such as wholegrains, pulses, nuts and seeds, and it’s likely you’ll lose a few kilos in the long run. The proof? A study team from the University of Texas reporting in The Journal of Nutrition looked at weight loss in a group of dieters.

Results showed fibre intake to be the strongest predictor of weight loss, with volunteers who ate an average increase of 4g of fibre more each day than when the study started losing an extra 1.5kg of weight over six months. What’s more, the higher-fibre eaters were much more likely to stick to their diets for the study’s duration. That’s some sustainable health and weight loss news we can absolutely get behind.

Expert ways to remake your plate

With fasting plans such as the 16:8 diet, there’s a lot of freedom in terms of what kinds of foods you can consume in your eating window. However, don’t expect to see a lot of change in your weight if you’re still dining out on fast food and high-sugar snacks. So what’s the ideal plate of food to maximise the weight-loss effects of the 16:8 schedule?

“With this variety of intermittent fasting, there are no caloric restrictions, so I’d simply encourage you to focus on ramping up the nutritional quality of your meals,” explains dietitian Melissa Meier. You also want to go for meals that offer lots of good nutrition and will keep you feeling full for hours (so you don’t get hungry during the fasting period). Here’s how.

Research has found fibre intake to be the strongest predictor of weight loss. Image: Getty

Hydrate early and often

To stay focused during your fasting period, drink water consistently throughout the day. Aiming for two litres will not only settle mild hunger pangs but also help swerve dehydration. Throw in lemon, lime or a few berries to up the interest factor.

Eat plenty of protein 

Lean protein sources will keep you powering through to the afternoon; fish, poultry, lentils and tofu are all good ways to score more. Try having eggs as your first meal, and adding a serving of chicken or tofu with your larger meals.

Stock up on fibre 

It’s one of the fastest ways to banish bloating, boost gut health and balance hunger hormones. Make sure you have a good serving of fruit and veg across your meals (which are packed with fibre), as well as wholegrains like quinoa, brown rice, oats and barley.

Embrace healthy fats 

Add healthy fats to further help with satiety in the form of avocados, olive oil, nuts and seeds. Avocado on wholegrain toast to start the day or a nutty granola mix for breakfast will not only keep your blood sugar stable, but keep you feeling fuller for longer.

Originally published as Everything you need to know about the 16:8 intermittent fasting diet