What is 16:8 Intermittent Fasting? Our Intermittent Fasting Guide

 Let’s be honest, the idea of fasting doesn’t sound like the most appealing prospect – particularly if you’re a grazer. However, if weight loss or recomp is your goal; don’t knock it til’ you’ve tried it!

You may already be familiar with 5:2 fasting; the diet whereby you restrict your calorie intake to 25% of your calorie needs (generally 500 calories a day or less) for two days a week and eat normally the rest of the time. This way of eating has been hailed for its weight loss benefits amongst many other health benefits such as reduced insulin resistance.

16:8 fasting has gained a lot of notoriety in recent years, one of its most famous followers is Hugh Jackman who credits 16:8 fasting for getting his physique Wolverine ready; and that six pack speaks for itself!

So, what exactly is 16:8 fasting?

On the 16:8 diet, you spend 16 hours a day consuming nothing but unsweetened beverages such as water, tea and coffee. The remaining 8-hour window of time is when you consume all your meals and snacks for the day. Many people choose to do this by starting their fast in the evening, skip breakfast and eat their first meal of the day around lunch time. One of the benefits of this way of eating is that no foods are off limits, however some people choose to combine 16:8 fasting with the keto diet to give their weight loss an extra boost. This cycle can be repeated as often as you like, from just one or two days a week or every day; it’s your personal preference. 

Yes, 16 hours without food may sound like torture – we know! But before you dismiss it entirely, it’s worth bearing in mind that many people choose to have their 8-hour eating window between 10-6 or 12-8 (depending on whether you’re a breakfast person or not), which still leaves you plenty of time to eat at a sociable hour and ensures you’re sleeping your way through a significant chunk of the fasting period!

What are the benefits of 16:8 fasting?

While many diets come with a set of strict rules and regulations to follow; 16:8 fasting takes minimal effort and couldn’t be easier to follow once you’ve selected your chosen 8-hour feeding window. 16:8 fasting is generally considered to be much more flexible and less restrictive than a lot of other diets as it can be easily incorporated into any lifestyle. Here are some of the health benefits to be gained by 16:8 fasting:

• Increased weight loss:  

By restricting your calorie intake to a few hours a day; you will not only help to cut calories over the duration of the day, but studies have also found that fasting can actually boost your metabolism and increase weight loss (2, 3, 4).

• Improved Insulin Sensitivity (Blood Sugar Control):

Intermittent fasting has also been shown to reduce fasting insulin levels by up to 31% and lower blood sugar by 3–6%, potentially reducing the risk of diabetes (1).

• Enhanced longevity: While evidence in humans is limited, several animal studies have found that intermittent fasting may extend longevity (5).

Is fasting for 16 hours actually healthy?

In a word, yes. However, if it is not recommended for pregnant or breastfeeding women or those trying to conceive. 16/8 intermittent fasting is simple, safe and sustainable. It is also not recommended for anyone with hormone imbalances, diabetics or anyone with an eating disorder or a BMI under 18.5 (6).

Is 16:8 fasting suitable for me?

Essentially, it comes down to your personal preference, lifestyle and eating style.

16/8 intermittent fasting can be a sustainable, safe and easy way to improve your health when paired with a nutritious diet and a healthy lifestyle. It therefore should not be considered a substitute for a balanced diet as it’s important to include healthy whole foods to remain healthy and achieve the best results.

If you are a grazer by nature and find yourself picking throughout the day and into the evening, this type of diet may not be for you. This being said, it’s certainly worth giving it a try and seeing how you find it as you may be surprised how satiated you feel just by staying hydrated during the fasting period.

The only real effort involved with 16:8 fasting is deciding when you’re going to have your 8-hour feeding window and sticking within it. Having to think about when you are eating can also provide additional benefits to your health (and waistline) than those mentioned previously. By being more restrictive with when you are eating, you may find yourself turning down ‘mindless’ snacking opportunities as they come your way.

 Here are some factors to consider when following the 16:8 diet:

The time of day that you train:

If you prefer to train first thing in the morning, let’s say 6-7am, so need to refuel after; this would mean starting your 8-hour feeding window at 7am and therefore not eating any more after 3pm. It’s likely that you would find yourself feeling hungry before bedtime if this were the case, particularly if you are socializing with other people that would be eating their evening meal while you go without. If it’s more suitable, you may also decide to train  during your lunch hour or in the evening which will still enable you to fast up until 11am/12pm and still eat an evening meal post-workout before the window closes 7pm/8pm.

Where you physically are when you choose to eat:

Most of us tend to eat based on the situation we are in rather than our hunger levels. For example, a trip to the cinema may lead us heading straight in the direction of the popcorn and pick ‘n’ mix; regardless of whether we are actually hungry or not… it’d be rude not to, right?

By being mindful of the moments you eat, you may actually become aware of eating patterns/habits you didn’t even realize you had.  Say you love a late-night graze watching Netflix or a grab a pastry with your coffee on the way to work; If you’re fasting starts at 8pm through to 12pm, these snacking habits will be automatically cut – along with their calories – bonus!

The amount of sleep you are getting:

When we are tired, its common to snack and eat more than usual in an attempt to give ourselves a boost of more energy. However, by giving yourself a set feeding window and fasting period, it’s likely you will find yourself going to bed earlier to avoid the temptation to snack if you are feeling peckish late in the evening. This will not only make your diet more effective; you will also reap the rewards of catching those extra Z’s. You will be allowing your body more time to rejuvenate and repair both mentally and physically and wake up feeling refreshed. Getting 7 hours kip has been linked to a reduced risk of chronic disease, improved metabolism and better weight management – so it’s a no brainer if you’re trying to lose weight!

How often should I do 16:8 fasting? 

If your goal is to lose weight or simply develop healthier eating habits, 16:8 fasting can be incorporated into your lifestyle one day a week (or several days, some people choose to do one day on, one day off). You may also choose to follow 16:8 fasting for a solid week or two week period and then gradually reduce this once you start to see results. 

This being said; providing you are eating a balanced and nutritious array of foods during your 8 hour window, 16:8 fasting is safe, sustainable and flexible enough to become a full-time eating strategy. If you find this way of eating agrees with you and is helping you towards achieving your desired body goals, there is no reason why you shouldn’t continue to eat this way as long as you wish to. However, see our tips further in this article to ensure you are fasting healthily and safely.

Can I really eat anything I want when 16:8 fasting? 

Not entirely, no. It is not recommended to eat junk food or binge eat when following the 16:8 diet. As there are no set rules about the types of food you must eat, this doesn’t give you free reign to eat anything and everything in sight – sorry! It does however allow you to have the occasional treat and eat a wide range of different food groups. High-fat and high-sugar foods should still be eaten in moderation, however they are not off limits and can be enjoyed as a treat providing you are still adhering to your daily calorie goals. Work out your daily calorie intake here with our TPW Calorie Calculator to ensure you adhere to your daily calorie goal and achieve your weight loss goals with ease!

Can I drink alcohol while 16:8 fasting? 

While alcohol is not strictly off limits, drinking during 16:8 fasting may scupper your weight-loss efforts. During the fasting period, you should not eat food or consume any beverages other than unsweetened water, tea and coffee, so by drinking alcohol (which is calorific) you are breaking your fast by giving your body a heap of calories during the period you should be fasting. This being said, drinking in moderation during your 8-hour feeding window is perfectly fine and won’t undo your hard work. 

One of the main benefits of intermittent fasting is its ability to boost fat burn, whereas alcohol has been shown to have the opposite effect. Alcohol also lowers our inhibitions and can lead us to make poor choices when it comes to food; yes that family bag of snacks with a bottle of wine or 2am takeaway after a night out, we’ve all been there. So you may want to cut down or cut out the booze while following 16:8 fasting if your main motivation is weight loss as it could possibly interfere with your results (3, 7).

How do I get started?  

First and foremost, pick an 8-hour eating window which you think will suit you and your lifestyle best.

As discussed, many people opt to keep their eating window between 12pm and 8pm as this means you will sleep through a significant chunk of your fasting period and only need to skip breakfast. This also allows you to still eat a balanced lunch and dinner at sociable hours that can fit in with family/friends. You will also be able to snack throughout the day once the clock strikes 12 at noon through to 8pm. 

Some of the early birds amongst us choose to eat between 9am and 5pm, this allows for a healthy breakfast in the morning, a normal lunch and an early evening meal or snack before the fasting period begins at 5.

Its recommended to experiment and choose a time frame that best fits your schedule and lifestyle.

To further boost the potential health benefits to be gained from 16:8 fasting, it’s recommended to stick to a nutritious well-balanced diet containing whole foods and ensure you stay hydrated throughout your fasting period and eating window.

Try balancing your meals with a good variety of healthy whole foods, such as:

•         Fruits: Berries, bananas, kiwis, apples, oranges, peaches, pears, etc.
•         Veggies: Broccoli, sweet potatoes, leafy greens such as spinach and kale, cauliflower, tomatoes, etc.
•         Whole grains: Quinoa, whole grain rice, oats, buckwheat, barley etc.
•         Healthy fats: Olives, olive oil, avocados and coconut oil
•         Sources of animal protein: lean red meat, poultry, oily fish, legumes, shellfish, eggs, dairy, etc.
•         Sources of plant protein: legumes, pulses, nuts, seeds, etc.

Drinking unsweetened beverages such as water and unsweetened tea and coffee, even while fasting, can also help control your appetite while keeping you hydrated.

While there are no set rules about the type of food you can eat on the 16;8 fasting diet, if you overdo it on junk food  and sugary drinks during your feeding window, you can actually undo the positive effects associated with 16:8 and could end up causing more harm than good to your health. Like any healthy diet, its all about balance and as long as you ensure you are eating good quality whole foods (as mentioned above) the odd treat will not do you any harm at all.

Are there any downsides to 16:8 fasting?

As we have discussed, there are many health benefits to intermittent fasting and it is very safe, however it may bring some drawbacks for some people and may not be the right diet for everyone.

•   16:8 fasting may cause short-term issues such as hunger and feeling tired/weak, however this would likely subside once you get into a routine and could just be from the drastic change of eating style, particularly if you were previously a grazer.
•    As your feeding window is restricted to 8 hours a day, this may lead some people to eat more than usual within this period of time, trying to compensate for the hours spent fasting. This could potentially lead to weight gain, digestive issues and developing unhealthy binge eating habits.

It is therefore recommended that you start 16:8 fasting gradually and if you have any concerns or experience any issues or negative symptoms you should speak to a doctor and return to your former way of eating.

The take home:

16:8 intermittent fasting has become a popular diet because it is super simple to follow, flexible and sustainable in the long term. It’s also very convenient, as it can cut down on the amount of money and time that you need to spend in the kitchen preparing food every week.

It’s recommended to speak with a nutritionist or doctor before trying intermittent fasting, particularly if you have any underlying health conditions. For best results it’s recommended to eat a healthy diet during your eating window and drink plenty of unsweetened beverages such as water, tea and coffee to stay hydrated; this will also help you to feel less hungry during the fasting period as a lot of time feelings of hunger can be from dehydration.

Reference List:

1. Barnosky, Adrienne & Hoddy, Kristin & Unterman, Terry & Varady, Krista. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: A review of human findings. Translational Research. 164. 10.1016/j.trsl.2014.05.013.
2. Byrne, Nuala & Sainsbury, Amanda & King, N & Hills, Andrew & Wood, Rachel. (2017). Intermittent energy restriction improves weight loss efficiency in obese men—The MATADOR study. International Journal of Obesity. 42. 10.1038/ijo.2017.206.
3. Cains, Sarah & Blomeley, Craig & Kollo, Mihaly & Rácz, Romeo & Burdakov, Denis. (2017). Agrp neuron activity is required for alcohol-induced overeating. Nature Communications. 8. 14014. 10.1038/ncomms14014. 
4. El Khatib, Sami & Yassine, Aya. (2019). Insights Gained from Intermittent Fasting & its Impact on Weight Management. International Journal of Science and Research (IJSR). 8. 1734-1743. 10.21275/ART2020639.
5. Ganesan, Kavitha & Habboush, Yacob & Sultan, Senan. (2018). Intermittent Fasting: The Choice for a Healthier Lifestyle. Cureus. 10. 10.7759/cureus.2947.
6. Goodrick, Charles & Ingram, Donald & Reynolds, Mark & Freeman, John & Cider, Nancy. (1982). Effects of Intermittent Feeding Upon Growth and Life Span in Rats. Gerontology. 28. 233-41. 10.1159/000212538.
7. Malinowski, Bartosz & Zalewska, Klaudia & Węsierska, Anna & Sokołowska, Maya & Socha, Maciej & Liczner, Grzegorz & Pawlak-Osińska, Katarzyna & Wiciński, Michał. (2019). Intermittent Fasting in Cardiovascular Disorders—An Overview. Nutrients. 11. 673. 10.3390/nu11030673.
8. Raben, Anne & Agerholm-Larsen, Lisa & Flint, Anne & Holst, Jens & Astrup, Arne. (2003). Meals with similar energy densities but rich in protein, fat, carbohydrate, or alcohol have different effects on energy expenditure and substrate metabolism but not on appetite and energy intake. The American journal of clinical nutrition. 77. 91-100. 10.1093/ajcn/77.1.91.