Changing the 16/8 Eating Window

Find out why changing your 16/8 eating window may not be the best idea.
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The 16/8 diet seems to be one of the most popular forms of intermittent fasting. However, if you are changing times of your 16/8 eating window by too much and too frequently, you could be minimizing the benefits this dietary pattern can offer you.

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

The 16/8 diet is probably the most popular version of intermittent fasting because it’s easy to do and it can be extremely effective. 

However, because so many people have busy schedules or schedules that change frequently, being consistent with the eating window can prove to be a challenge. 

So what does this mean? Does it matter if you are consistent with the eating window or is changing times acceptable?

Read on to find out!

The 16/8 Diet

Before we talk about the consequences of changing times of your 16/8 eating window, first let’s define the 16/8 diet. The 16/8 diet is where individuals fast for 16 hours of the day and eat freely for the remaining 8 hours. The window they choose to eat is entirely up to them, meaning they can eat from 10am-6pm or 12pm-8pm, or any other variation!

This is probably the most popular form of intermittent fasting because it’s one of the easiest forms of fasting to adhere to and make a habit. The fasting window is relatively short compared to other forms like alternate-day fasting, one-meal-a-day (OMAD), and whole day fasting, which also makes it attractive. 

How Does the 16/8 Diet Work?

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One topic we should cover is how the 16/8 diet helps to mitigate disease risk while aiding in weight loss. 

While scientists still have a lot to learn, there is one aspect of the 16/8 diet (and intermittent fasting in general) that we know plays a huge role in how this diet improves your health status and that is your circadian rhythm. 

Your circadian rhythm is a natural bodily process that follows an approximate 24-hour cycle that coincides with the sun. One example of this rhythm is sleeping at night and being awake during the day.

Other aspects of your body follow this rhythm as well. For example, certain processes related to digestion and metabolism are upregulated during the day and downregulated during the evening. 

Humans, and most mammals, evolved to have this cycle as a way of preserving energy to maximize survival. In other words, your body evolved to downregulate certain processes during times of the day when you were less likely to use them as a way to conserve precious energy (1).

Studies have shown that disruptions to our circadian rhythm can increase our risk for certain metabolic disorders such as insulin resistance, hypertension, cardiovascular disease, and more (2, 3). 

One way to disrupt this system is by eating constantly throughout the day…or eating when processes related to digestion and metabolism are downregulated. This means that late-night snacking can disrupt your circadian rhythm and increase your risk for disease. 

A good example of this is individuals who work night shifts, like nurses. These individuals will sleep during the day and consume food during the evening, which disrupts their circadian rhythm. Studies have shown that shift workers tend to be at an increased risk of these metabolic diseases (2).

Interestingly, you can change your circadian rhythm a bit by having your body adapt to certain eating habits, and this happens when you adapt an intermittent fasting routine. 

For example, if you decide to try the 16/8 diet and your eating window is 11am-7pm, after a while, your body will adjust and you likely won’t feel hungry during your fasting window. But be patient because this can take a couple weeks. 

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What Happens When You Change Your 16/8 Eating Window?

4 clocks showing 4 different times.

This is a tough question to answer because to the best of our knowledge, there hasn’t been any studies that have investigated this. However, based on what we just described about the circadian rhythm, you are probably not reaping all of the benefits this diet can offer you.

If you are changing times by going outside of your window by a small amount, maybe a half hour or less, or if you go way outside your window every once in a while, you are probably fine. But if your eating window changes by more than 30 minutes and this happens regularly, you may want to rethink your chosen eating window. 

The way you mitigate disease risk through the 16/8 diet is by eating in a timeframe that aligns with your circadian rhythm and when pathways related to metabolism and digestion are upregulated. 

Consistency is key. Changing your 16/8 eating window regularly isn’t helping your health.


But don’t let this discourage you! You have options! Look at your schedule and see if you can change your eating window to accommodate your daily routine.

However, if your day-to-day schedule changes frequently, you may want to rethink if the 16/8 diet is the best form of intermittent fasting for you.

Great alternatives for people with busy and changing schedules are one-meal-a-day fasting or OMAD (eating one, big meal a day), alternate day fasting (fasting every other day), and whole day fasting (picking 1-2 day (s) a week where you fast completely). 

Check out our article about choosing the right fasting window for additional guidance.

If you are having trouble sticking to the 16/8 diet because you tend to give-in to temptation, that’s fine too because it just means you have to work on self-control. A good way to help with restraint is by joining a community and we’ve got one for you! 

Join our community of women who are doing various forms of intermittent fasting and are seeing results! Knowing other women like yourself are pushing through these temptations may help motivate you!

The Bottom Line

The 16/8 diet is a great form of intermittent fasting to help you achieve your health and weight loss goals. However, if you are constantly changing times of your eating window because of your busy schedule, you may not be getting all of the benefits this diet has to offer.

Think about if you can truly adopt this diet, and if not, try another form of intermittent fasting…there are many to choose from!


1. Paoli A, Tinsley G, Bianco A, Moro T. The influence of meal frequency and timing on health in humans: The role of fasting. Nutrients. MDPI AG; 2019. 

2. James SM, Honn KA, Gaddameedhi S, Van Dongen HPA. Shift Work: Disrupted Circadian Rhythms and Sleep—Implications for Health and Well-being. Curr Sleep Med Reports. Springer Science and Business Media LLC; 2017;3:104–12. 

3. Kyriacou CP, Hastings MH. Circadian clocks: genes, sleep, and cognition. Trends in Cognitive Sciences. 2010. p. 259–67.

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