18/6 vs. 16/8: Do Two Hours Really Make a Difference?

If you’ve heard about intermittent fasting – the practice of alternating extended periods of fasting with limited windows of feeding in order to achieve certain health outcomes – and all of its benefits – like giving you energy, helping you maintain a healthy weight, and boosting your mood – and decided to give it a try for yourself, you probably want to start out with one of the easier versions that is more accessible for beginners.

If that’s the case, the two most relevant options are 18/6 fasting and 16/8 fasting… but what’s the difference between them and their confusingly similar names? And does it actually matter which one you do? For answers to all these questions and more, read on.

What is 16/8 Fasting?

When an intermittent fasting style is named with numbers, like “#/#,” the first number refers to the period of time during the day that you’ll be fasting and the second number refers to the number of hours you have during your feeding period. So with 16/8 fasting, also referred to as leangains fasting, you fast for 16 hours a day and have an eight-hour eating window on a daily basis.

Of all of the recognized, structured types, this is the form of intermittent fasting that involves the shortest possible fasting window, making it most suitable for beginners. Typically, practitioners will skip breakfast and eat (healthily!) from noon to 8 p.m. Sounds surprisingly doable, right?

What is 18/6 Fasting?

According to the naming logic we defined earlier, it follows that 18/6 fasting involves 18 hours of fasting and six hours of eating in a typical day.

This type of fasting usually makes enough time for two meals and a snack every day, so people will generally eat a late first meal of the day and an early second. Because the eating window is shorter, it’s common for people to eat much larger meals than they would if they were not intermittent fasting at all.

It’s also worth noting that many people start out in intermittent fasting by trying out leangains (16/8) before eventually realizing they can push it a little further and moving onto 18/6.

Similarities Between 18/6 and 16/8 Fasting

As you can imagine, there are several notable similarities between 18/6 fasting and 16/8 fasting, including their incredibly similar names that make things a bit more confusing than is ideal. In fact, people often asks if it even matters which one they do. Well, here are a few things you can expect to experience with either of these 24-hour fasting styles.

First, they’re both easy ways to get started for an intermittent fasting beginner. If you’ve never tried intermittent fasting before, it’s highly recommended that you choose one of these two options as a way in rather than a more challenging fasting schema.

Another commonality is that both 16/8 and 18/6 are types of fasting that you can, in theory, do for the rest of your life. That is to say that they’re not something temporary and difficult to sustain that you do once a week like a 24- or 48-hour fast. Instead, they’re a way of fitting intermittent fasting into your daily routine and lifestyle. You can even plan ahead if you have a big event at a certain time of day, switching your eating window to a time that works for you on that particular day.

And happily, both of these styles will proffer you many of the benefits of intermittent fasting that you’re probably looking for. They’ll increase your levels of energy during the day, complement and enhance your strength training regimen, help you maintain a healthy weight or even lose some extra fat, make you feel peppier and potentially happier, and more.

Differences Between 18/6 and 16/8 Fasting

Now let’s talk about the major differences between 18/6 and 16/8 fasting and how much of a difference you can expect it to really make depending on which one you choose.

First, the meaning of that seemingly insignificant two-hour difference can be important for how many calories you take in. If you’re overweight and your main goal with intermittent fasting is to lose weight, having two fewer hours to eat every day can ultimately lead to you eating fewer calories every day, which can add up signifcantly over time.

On the other hand, if you know that you’re likely to get hungry easily or that fasting might be challenging for you mentally, getting two extra hours to eat in a day might make a big difference in how sustainable intermittent fasting is for you. After all, an eight-hour eating window isn’t actually that different from the way you might already be eating in your day to day life.

Finally, it’s worth discussing the difference in results that you might get from doing 18/6 fasting instead of leangains fasting. A study actually came out earlier this year on 16/8 fasting that sought to find out what its impact was on weight loss and metabolic health. And the results were rather surprising: a 16/8 diet was associated with a modest decrease in weight that wasn’t actually that different from the weight loss seen in the control group.

This is in direct contradiction to other studies that do show metabolic improvements and more weight loss in people doing intermittent fasting, like this one that showed a connection between intermittent fasting and increased stress resistance, increased longevity, and a decreased incidence of diseases, including cancer and obesity. The difference? This study looked at people doing 18/6 fasting.

The implication here is pretty clear: maybe the two-hour difference between 16/8 fasting and 18/6 fasting is actually very important for getting the benefits of intermittent fasting that lead people to even bothering with it in the first place.

Obviously, we’re not here to make any kind of definitive statement about which types of fasting are better and more effective or which you should do, if any. But this information might be worth considering if you’re trying to choose between 18/6 and 16/8 fasting. We hope you find it helpful!