The Simple, Striking Truth About Fasting Fluids
When folks ask me what they can drink while fasting, I don’t give them a complicated lecture. The answer is remarkably simple: Stick to non-caloric beverages and drink them to thirst. This framework is the key you can run most fasting-related beverage questions through. However, I understand that out of an abundance of caution, people often triple-check which drinks break a fast, regardless.
In my opinion, we’ve lost our sense of propriety and scale regarding fasting. Folks’ heads spin with terms like autophagy and mTOR without much context. Whether coffee breaks a fast is a semi-interesting debate topic, but it is not a mission-critical item that should deserve hours of careful consideration. Too often we get tangled up in the minutia and focus on the wrong questions.
I want to set the record straight: Fasting is NOT a binary proposition—it’s not just “on” or “off“—it’s a spectrum with different positions. A mere drop of coconut oil or honey is not going to undo all the benefits. Instead of arguing about tea, MCT oil, or even coffee, we should be talking about electrolytes.
This is the most compelling reason to emphasize a particular fluid choice. Why? Because fasting makes your body shed sodium like a young snake sheds skin—and believe me, it’s a lot. It is of the utmost importance to replace this salt.
Getting enough electrolytes can make the difference between feeling like a champ or a crusty, dried up sponge. Yes, fasting can be tough mentally and physically on the best of days, but inadequate electrolytes can be dangerous and downright miserable.
I can tell you from experience that this misery will not enhance the benefits in any way, shape, or form. Thankfully, it’s easy to get enough without having to break your fast. I’ll cover that later, but as a spoiler alert, the salt shaker and LMNT are both useful here. But first, we need to sync up on what fasting means and how it will influence your hydration needs—so keep reading.
Fasting Basics
To fast is to deny your body calories temporarily. That’s the basic definition. If this temporary break from food lasts under 36 hours, it’s considered an intermittent fast. If it lasts longer, it’s considered an extended fast. But must fasting be a zero-calorie affair? Not necessarily.
In fact, many fasting protocols allow for limited calories. For instance, the 5:2 or 5 days of regular eating then 2 non-consecutive fasting days per week is a popular intermittent fasting regimen that generally permits about 500 calories on fasting days. And Valter Longo’s Fasting Mimicking Diet (FMD) has shown clinical benefits and entails one 5-day stretch of similar calorie restriction per month. Those are the logistics.
So, why would people voluntarily sign up for such deprivation? To answer, let’s take a little trip back to 20,000 BC. Back then, humans didn’t fast because they heard a podcast—they fasted because the food kept running out. Yet, their bodies didn’t immediately shut down without food.
When berries and rabbits weren’t available, they would turn to another source of energy: body fat. Even in a lean human, this could last for days and sometimes weeks. What was a survival need then is a health intervention today. For individuals who are obese or diabetic, fasting can initiate a metabolic reset, resulting in weight loss, improved insulin sensitivity, reduced risk of heart disease, and overall better health.
Keep in mind, though, that more isn’t always better. It’s a stressful endeavor, and it pains me to see otherwise healthy folks suffering—bags under their eyes, sunken cheeks, and ashy skin—through extended fasts on a weekly basis. Specifically for lean, metabolically healthy people, I’m not sure how much upside there is vs., say, an additional strength training session each week. I’m currently in the minority on this, but I lay out this case in-depth in my talk, “Longevity: Are we trying too hard?”
In my experience, the sweet spot for most people is 13 to 18 hours of daily fasting. If you go beyond that, you should have a good reason for doing so. Again, there are tradeoffs between choosing more or, for example, some Zone 2 cardio and/or strength training.
Breaking vs. Maintaining a Fast
The Nuance of Breaking or Maintaining Your Fast
What does it mean to break a fast? It’s a simple question that requires a nuanced answer. You could say that consuming calories breaks a fast, but many fasting protocols show benefits from merely limiting calories. And besides, not all calories are created equal. The extent to which a food or drink “breaks a fast” hinges on two main factors: The number of calories consumed, and the type of calories consumed.
The first factor is fairly straightforward: The more calories you consume, the more likely you will disrupt the fast. The second thing to consider is the type of calories you eat. The more a food makes your body release insulin, the more it can throw off your health.
Here’s how macronutrients rank, from most to least disruptive to a fast: Carbohydrate, Protein, then Fat. Carbs, especially from refined sugar, are the worst because they cause the biggest insulin spikes. Carbs cause the greatest release of insulin, a hormone that tells your cells to store fat. Insulin then suppresses the fat-burning state called ketosis and therefore disrupts the central driver of fasting benefits, most notably the suppression of mTOR. Still, I must remind you that the dose makes the poison. A teaspoon of honey in your tea or electrolyte drink won’t ruin your fast.
Of course you could just as easily use stevia, but my point is that IF you want to use a splash of honey here and there, I do not see a problem. We’d do well to dispense with the nearly religious fervor that emerges around the nuance of fasting.
By contrast, fat has the smallest impact on the release of insulin and suppression of mTOR. That’s why adding MCT oil to your morning coffee won’t meaningfully interfere with your fast. However, I must remind folks that there are more calories in a gram of fat than a gram of carbs.
I have worked with folks who drink a ton of butter in their coffee, yet struggle to figure out why they are gaining weight and feel awful. Don’t get me wrong, butter is great. But we needn’t drink appreciable amounts of butter any more than we need to consume 1000 calories of sugar sweetened sodas each day.
Now that we’ve laid down some much needed nuance around fasting and calorie intake, let’s shift gears and focus on electrolyte needs while fasting. Don’t worry, this is much more straightforward and has a good bit less controversy surrounding it.
Staying Hydrated While Fasting
The Crucial Role of Electrolytes in Fasting Hydration
Most people are confused about how to stay hydrated while fasting. In general, they believe that drinking more water is better. Period. It’s not.Yes, fasting can make you lose more water through urine.
But just drinking plain water to make up for it isn’t the best way. It’s a poor strategy because in addition to losing water, you’re also losing electrolytes at a higher rate while fasting.
And if you only replace the fluids, it can exacerbate the electrolyte imbalance. Specifically, drinking plain water beyond thirst has the potential to dilute blood sodium levels. Add this to amplified urinary sodium losses, and you have a formula for hyponatremia. Hyponatremia is the medical term for low blood sodium.
The symptoms include headaches, fatigue, weakness, muscle cramps, confusion, and—in severe instances—seizures, brain damage, and death. You often see hyponatremia in elite endurance athletes, who sweat out tons of sodium and drink plain water on a set schedule despite a lack of thirst. I think there’s a lesson to be learned here that folks can apply to their fasting regimen. The key takeaway is simple: pure water isn’t enough when your body is aggressively flushing out essential minerals. Now that you understand the basics of fasting hydration, let’s cover some specific fasting-friendly beverages to help you avoid this dangerous pitfall.
What Can You Drink While Fasting?
Fasting-Friendly Fluids: A Quick Guide
Don’t agonize over this question. If you’re drinking a non-caloric beverage to thirst, it’s generally fine. And if the beverage contains a little bit of fat, that’s not a huge deal either. While fasting, you’ll want to avoid high-sugar, high-calorie drinks like: Soda, Fruit juice (even if there’s “no sugar added”), Sugary sports drinks, Milk, chocolate milk, and hot chocolate, Smoothies, Protein drinks, Alcoholic beverages, and Most latte, cappuccino, mochaccino, and frappuccino drinks. That’s the basic gist, but let me expand on these common questions because I see them every day.
Can I drink water while fasting? Yes, just drink to thirst and make sure you’re getting enough sodium. I must caution you: “Dry fasting” will cause dehydration. I don’t recommend it unless you really know your stuff. Regarding black coffee, I say, go for it. Coffee contains loads of antioxidants and may enhance a fasting-induced cellular recycling program called autophagy. The funny thing about coffee is that it enhances autophagy whether or not you are fasting. Similarly, Can I drink tea while fasting? Yes. No calories, lots of antioxidants.
Now for the complex ones: Can I drink diet soda while fasting? I suggest looking for a soda that has no calories and is sweetened with stevia or monk fruit instead. Artificial sweeteners like aspartame and sucralose aren’t very insulinogenic, but they may have funky effects on gut bacteria. Can I drink bone broth while fasting? A mug or two of bone broth shouldn’t meaningfully disrupt your fast. It does contain a bit of collagen protein, but the amino acid profile (glycine, proline, etc) is fasting-friendly. Finally, and critically: Can I drink electrolyte water while fasting? Please do, provided the electrolyte drink doesn’t contain sugar.
The Importance of Drinking Electrolyte Water
The Single, Essential Rule for Hydration
I can explain most of what you need to know about hydration in one sentence. This principle covers fasting hydration, keto hydration, endurance hydration, strength hydration, and, most importantly, everyday hydration. If you follow this rule, you’re good in 95% of hydration situations. And it’s not hard to follow. The rule is: Drink electrolyte water to thirst.
Drinking electrolyte water to thirst ensures you replace lost electrolytes AND lost fluids. It not only prevents dehydration but also the dangerous consequences of overhydration. For me, LMNT is my science-backed answer to this need. This tasty electrolyte drink mix is zero sugar, zero junk, and totally fasting-friendly. Just 1-2 sticks during your fast (1-2 grams of sodium) can make a massive difference. Thousands of people have felt this difference, including professional athletes, which is partially why LMNT has caught on in such a big way.
Of course, LMNT isn’t the only way to get electrolyte water. It’s just convenient and tasty. You can check out this article for more ideas. But compared to other products, it’s the only mix with enough sodium to move the needle.
To wrap up, when it comes to fasting hydration, electrolyte water is the answer. I like when the best solution turns out to be a simple solution, don’t you?