Intermittent Fasting? Find Out What Really Breaks Your Fast

Diets can get a bit tiresome. All that telling you what you can and can’t eat, right? So maybe you’ve changed tactics, and have settled on an “eating protocol” instead of a diet, which probably means that you’re doing intermittent fasting, or IF. So if you’re on the IF train, you know that this type of eating protocol doesn’t necessarily dictate what you eat (like keto or paleo, for example), although it’s suggested that you should still eat a healthy diet to get the most benefits, it’s instead all about when you eat. Ok, sounds simple enough, but you might still have questions about what you can put in your mouth (if anything at all) during your fasting time, so read on for a handy guide to what breaks your fast. 

Intermittent Fasting Options

While studies are still being done on intermittent fasting, it’s become popular as a weight loss tool, as well as one for boosting health, since the studies we do have suggest that IF promotes ketosis (and thereby increases fat burn), boosts cognitive functioning, reduces inflammation, and might even boost longevity. 

And it’s definitely not one size fits all, which is another reason it’s become so popular. You have different options for how to set up your IF schedule, depending on what works for your body and lifestyle. 

For example, you can try:


  • Time-restricted eating – This eating pattern involves fasting every day for 12 hours or longer and eating in the remaining hours. A popular example is the 16/8 method, which means that you have a daily 16-hour fast and an 8-hour eating window, during which you can fit in 2, 3, or more meals.
  • The 5:2 diet – The 5:2 diet involves eating as you normally do 5 days of the week, and restricting your calorie intake to 500–600 on the remaining 2 days.
  • Eat Stop Eat – Eat Stop Eat involves a 24-hour fast once or twice per week.
  • Alternate-day fasting – With alternate-day fasting, the goal is to fast every other day.
  • Meal skipping – This type of IF is generally good for beginners, since it involves choosing one meal a day to skip.
  • The Warrior Diet – On the other hand, this type of IF is a little more extreme, and probably better for people who have tried other types of IF already. It involves eating minimal amounts of raw fruit and veggies during the day and eating one large meal at night. 

What Breaks a Fast? 

So if one of these types of eating has become your cup of tea, what should your fast look like? Can you, for example, have an actual cup of tea during your fasting window? Let’s look at what actually breaks a fast according to experts, what kind of flexibility you might be able to add to your fasting routine, and what you should definitely avoid.

Can you have any calories during a fast?

First of all, when we say “fast,” how strict are we talking? Can you have more than just water, one of the only true calorie-free things that we consume? Experts are actually a bit split on this question, and tend to talk about this debate in terms of two of the known and sought-after benefits of IF: ketosis and autophagy:

  • Ketosis is a process that happens when your body doesn’t have enough carbohydrates to burn for energy, so it burns fat and makes things called ketones, which it can use for fuel. In other words, putting your body into ketosis (which is also the goal of the “keto” diet), increases fat burn.
  • Autophagy is the body’s way of cleaning out damaged cells, in order to regenerate newer, healthier cells. This process is less on the weight loss side of IF, and more on the health boosting side (although losing weight will boost your health, as well!)

Talking about these processes, which are the goals of IF, is where things get a little unclear when it comes to how many – if any – calories you should be consuming during a fast. Some experts, like Benjamin Horne, Ph.D., a genetic epidemiologist who has published research on the effects of intermittent fasting, say that while “technically, consuming any calories breaks a fast,” ketosis might actually remain active with the consumption of certain macronutrients (or carbs, fat, and protein). According to Horne, “One mechanism that is known to remain active when a small amount of food is consumed is ketosis—as long as you consume less than 50 grams of carbohydrates [in a day].”

Autophagy, on the other hand, seems a little trickier. According to Horne, “In humans, it appears that autophagy does not remain as active when any food is consumed.” He thinks that even the 2-5 calories in a cup of black coffee could throw the process out of whack; other experts aren’t so sure, though.  

Says Vincent Pedre, M.D., an integrative physician and gut health expert, “I’ve heard good debates about whether coffee can break a fast. We don’t have any good evidence to show either way. I would say if you’re drinking organic black coffee—no cream, no sweeteners—then you should be fine. That said, I would say stick to as close to zero calories as you can during your fasting hours with plenty of clean filtered water; herbal teas are also good.”

Is “dirty fasting” the key to consistency?

water with lime in it
Clean fasting is when you eat minimal calories during your fast.

Unfortunately, we can’t give you any definitive answer about having any calories at all during your fast, but it seems as though getting close to zero calories should be your goal if you want to get the full benefits of your fast. You probably know that already, though, and maybe it’s been holding you back from going no holds barred on intermittent fasting – which in turn is keeping you from getting any benefits at all! 

So, with that being said, some experts actually recommend consuming small amounts of calories from certain foods, if the choice is an all-or-nothing one between water-only fasting and not staying consistent with your IF at all. So, if you’re not sure that “clean fasting” is something you can stick with, you could consider what’s known as “dirty fasting.” Check out the difference:

  • Clean fasting means that you are consuming the minimal number of calories that you can during your fast, by generally sticking to water or other noncaloric beverages. 
  • Dirty fasting is a form of modified fasting that allows the addition of a certain number of calories during the fast. Experts don’t fully agree on what is the best way to do a dirty fast, but many say that you should stick to foods under 100 calories that are high-fat and won’t spike blood sugar. For example, integrative physician Amy Shah says of her own dirty fasting method, “For me, I like to fast as long as possible with just water—that might be 13 or 14 hours of a water fast—then I’ll have my tea with almond milk (the start of my ‘dirty fast’) and end at around 16 hours.”

Dirty fasting is definitely an option if it’ll keep you happy and consistent, just keep in mind that fewer studies have been done on this type of fasting. According to Samantha Cassetty, M.S., RD, nutrition and wellness expert, “keep in mind that there are almost no studies on this form of fasting, and without evidence, we can’t say whether this modified fasting protocol would produce similar benefits as might be experienced through other intermittent fasting protocols.”

If you’re going to consume calories, where should they come from?

If you’ve decided that you are going to consume some calories during your fast to help keep you on the intermittent fasting train, it’s not only important to remember that there are fewer studies on the effects of that type of fasting, but also that you shouldn’t just be grabbing whatever’s in reach. When we say “dirty fast,” we don’t mean it’s time to bust out the Oreos! 

There are some things that have calories (and therefore technically break your fast) that might still allow you to get some of the benefits of IF. For example:

  • Tea and coffee – Yes, these innocuous, water-based hot drinks technically have a few calories! That means they might (MIGHT) throw you out of autophagy, but that’s not even all that clear. In fact, in studies with mice, it looked like coffee actually induced autophagy, so we’re going to give that one a big shrug. And, since these drinks don’t seem to interfere with ketosis, and in some cases, coffee can even have an appetite-suppressing effect, we’re going to give the thumbs up to some black coffee or a comforting cup of tea.
  • Certain fats – Just like you can choose to do a dirty fast, you can also choose to do a “fat fast,” or one that includes hot drinks blended with fats like coconut oil, ghee, or grass-fed butter. This type of fasting is recommended less for weight loss. According to integrative dietician Ali Miller, R.D., “Low body fat levels can drive imbalances in hormones, so a ‘fat fast’ would be appropriate for people looking for moderate body composition changes or maintenance,” But it certainly won’t be bad for your waistline: this type of fasting allows you to push off hunger and cravings (so you don’t eat a full-blown meal) and allows for ketosis, so it is still good for maintaining a healthy weight. Plus a little fat (especially in the morning) helps keep you regular! You might not get the full benefits of autophagy, though, since you will be breaking your fast.person holding a mug full of broth
  • Bone broth – Again, bone broth does have calories, so it will technically break your fast, but even renowned IF expert Jason Fung, M.D. says a bit of bone broth is a great way to keep you on track, while giving you the electrolytes and minerals that your body might need during a longer fast. Consuming water alone, especially if your fast is longer than 16 hours, can reduce electrolyte levels in the body, leading to potential complications such as low blood pressure, confusion, nausea, muscle spasms, and fatigue. Just be careful with too much bone broth, as it seems to interfere with autophagy (as a lot of protein does). 

Is there anything you definitely shouldn’t have? 

A lot of things are off the table during your fasting window, but there is one little thing that you might not even be worrying about, which experts say to avoid on IF: artificial sweeteners. Yes, they technically have zero calories, but experts pretty much agree that just because something doesn’t have any calories, doesn’t mean it doesn’t affect your body. 

According to Miller, “Just because something is noncaloric doesn’t mean it is free of metabolic influence. The taste of sweet impacts GLP-1 receptors on the tongue, which enhances insulin release—this is not ideal, as insulin has a negative impact on fasting and may drive blood sugar drops.” And blood sugar spikes are exactly what you’re trying to avoid while fasting!

If you’re doing intermittent fasting, hopefully it’s feeling like the right alternative to traditional diets to you, and you’re feeling good! But if you’re also feeling confused about the “right” way to do it, know that there is some flexibility – and also remember that the way you choose to eat should make you feel good. If you feel like you can’t do the whole full-blown water fast thing, you can try one of the above alternatives if it’ll keep you happy and consistent. But you can also try tweaking what you’re doing during your feeding window: make sure you’re eating enough and eating the right foods. Bottom line: do what works for you! And make sure you tell us how your IF journey is going!

Co-written by Joanna Bowling

About The Author:
Cassandra Love

With over a decade of helpful content experience Cassandra has dedicated her career to making sure people have access to relevant, easy to understand, and valuable information. After realizing a huge knowledge gap Cassandra spent years researching and working with health insurance companies to create accessible guides and articles to walk anyone through every aspect of the insurance process.

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