The Bare Bones on Fasting The quick answer
A bone broth fast means drinking mostly bone broth for a set window instead of eating solid food. Because broth has some calories and protein, it is best understood as a gentle, modified fast rather than a true water fast, so whether it breaks your fast depends entirely on your goal.
- A bone broth fast replaces solid meals with broth for a set window.
- It is a modified fast: broth has calories and protein, so it is gentler than a water fast.
- Does it break a fast? For a strict water fast, yes. For a modified or intermittent fast, usually no.
- Fasting itself has real, if short-term, evidence for weight and metabolic health.
- Not for everyone: skip it if pregnant, nursing, diabetic, or with a history of disordered eating.
A bone broth fast sits somewhere between eating normally and a strict water fast, which is exactly why it raises so many questions. Here is what it actually is, where the idea comes from, an honest answer to whether it breaks a fast, what the fasting research really shows, and who should not try it.
What Is a Bone Broth Fast?
A bone broth fast means drinking mostly bone broth, in place of solid meals, for a set window, anywhere from part of a day to a full day or two. The appeal is straightforward: broth provides warmth, sodium, and a little protein, which makes going without solid food far more comfortable than water alone. The modern version was popularized by Dr. Kellyann Petrucci, MS, ND, who built her bone broth diet around broth-based “mini-fasts” designed to deliver the benefits of fasting “without the pain.” That phrase captures the whole point: broth is the tool that makes fasting sustainable for people who could never manage a water fast.
Does Bone Broth Break a Fast?
The honest answer is that it depends entirely on your goal, so it helps to break the question down by what you are fasting for.
So for a purist water fast, yes, broth breaks it. For the far more common goals, weight management, curbing appetite, and time-restricted eating, the small number of calories in a cup is usually fine, and many people find broth is exactly what makes an intermittent fast sustainable.
What Fasting Research Actually Shows
Set the broth aside for a moment, because the interesting evidence is about fasting itself. According to the National Institute on Aging, hundreds of animal studies and a number of human trials suggest intermittent fasting can improve conditions like obesity, diabetes, and cardiovascular risk. The same source is careful and honest: the human trials have mostly been short-term, so long-term effects, including on lifespan, are not established.
The mechanism is worth understanding, because it explains why timing matters. The landmark New England Journal of Medicine review describes how, after roughly 12 hours without food, the body depletes its easily-accessed sugar stores and flips a metabolic switch, from running mostly on glucose to breaking down fat and producing ketones for fuel. Those ketones are not just an energy source; they act as signaling molecules that appear to influence stress resistance and metabolism. This is the real, cellular reason people fast, and it is also why a fast generally needs to run beyond about twelve hours to do much.
Autophagy: The Honest Version
You will often see bone broth fasts linked to autophagy, the cellular housekeeping process in which cells break down and recycle their own worn-out parts. It is a real and important process, and fasting can promote it. But two honest caveats matter. First, the strongest evidence for fasting-induced autophagy comes from animal studies, and the NEJM review presents it that way; the human evidence is still preliminary and hard to measure directly. Second, and more specific to broth: because a bone broth fast provides calories and, in particular, protein and amino acids, it is a modified fast, and it likely does not trigger the same deep autophagy that a true water fast would. The fair, honest claim is that a broth fast is gentle and sustainable, not that it maximizes autophagy.
Why People Choose Broth Over a Water Fast
For most people, the point of using broth is simple tolerability. Fasting on water alone is genuinely hard, and it is where many people fail. A warm, salty cup of broth replaces some of the sodium and fluids you lose while fasting, delivers a small amount of satisfying protein, and is far kinder to your energy and mood than an empty stomach. Clinical dietitians recognize broth as a useful tool in exactly these situations.
“Bone broth is not a substantial source of calories and protein.”
L.J. Amaral, clinical dietitian, Cedars-Sinai
That low-calorie quality is the whole point here: it is enough to make fasting comfortable, without being a meal. It is the reason a broth-based mini-fast succeeds for people who could never stick to water alone.
How to Do a Bone Broth Fast Sensibly
If you are cleared to try one, keep it simple and short. Pick a modest window to start, such as a partial day or a single day, and drink bone broth whenever hunger hits, along with plenty of water and unsweetened tea. Choose a lower-sodium broth if you are sipping several cups, listen to your body, and break the fast gently with a light, whole-food meal rather than a large one. Do not stack fasting days back to back when you are new to it. For the everyday how-to of drinking and storing broth, see how to use bone broth, and to see how the fast fits a wider plan, see the bone broth diet.
Who Should Not Do a Bone Broth Fast
This is the section that matters most. A bone broth fast is not right for everyone, and for some people it is genuinely unsafe. Do not attempt it during pregnancy or breastfeeding, or if you have a history of disordered eating, where fasting can do real harm. People with diabetes, or anyone taking medication that affects blood sugar or blood pressure, should be especially cautious, since fasting can cause blood sugar to drop, and the same goes for anyone managing a medical condition or who is underweight. Children and older adults have different needs and should not fast without guidance. If any of this applies to you, or you are unsure, talk with a qualified healthcare professional first. And remember that your liver and kidneys, not the broth, handle detoxification. This page is information, not medical advice.
Types of Bone Broth Fasts
Bone broth fasting is not one thing. People do it in a few different ways, and the right one depends on your experience and goals. The gentlest is a daily, intermittent-style approach, where you simply narrow your eating window and use broth to get through the fasting hours, which is the most sustainable for everyday use. A step up is a single 24-hour broth fast, done occasionally, drinking only broth, water, and tea for a full day. The most demanding is a multi-day broth fast of two or three days, which some people use as a periodic reset, but which carries real risks and should only be done with professional guidance. If you are new to this, start at the gentle end and stay there until you know how your body responds.
What to Expect Hour by Hour
It helps to know roughly what is happening as the hours pass. For the first several hours, your body runs on the sugar stored in your liver, and you may feel fairly normal, with hunger coming in waves rather than steadily. Somewhere after about 12 hours, as those stores run down, the body begins shifting toward burning fat and producing ketones, the metabolic switch the research describes. Hunger often eases once that shift is underway, though it can feel worse right before it. A warm cup of broth at the moments hunger peaks is the simplest way to ride through them. Mild lightheadedness, a dip in energy, or irritability can happen, especially early on, and broth’s sodium helps blunt them. Anything more than mild is a signal to stop and eat.
How to Break a Bone Broth Fast
How you end a fast matters as much as the fast itself. Break it gently with a small, whole-food meal rather than a large or heavy one, since a big meal on an empty stomach can leave you uncomfortable. Something light and protein-forward, with some vegetables, is ideal, and it is worth giving it an hour or two before you eat a full-sized meal. The longer the fast, the more careful and gradual the refeeding should be, which is one more reason to keep bone broth fasts short unless a professional is guiding you.
Bone Broth Fast vs. Water Fast vs. Juice Cleanse
It helps to place the bone broth fast next to its neighbors. A strict water fast is the deepest and most demanding: nothing but water, which pushes the metabolic switch and any autophagy furthest, but which is the hardest to sustain and the riskiest to do for long. A bone broth fast is the gentle middle path: it gives up a little of that depth in exchange for warmth, sodium, and a small amount of protein that make it genuinely doable, which is why so many people succeed with it where they failed on water. A juice cleanse is a different animal entirely, and a misleading one, because fruit juice is high in sugar, which keeps insulin up and prevents the very metabolic shift that fasting is meant to produce. Of the three, the broth fast is the one most people can actually stick to, and it does not spike your blood sugar the way a juice cleanse does.
Frequently Asked Questions
Does bone broth break a fast?
It depends on your goal. Because broth has some calories and protein, it breaks a strict water fast. For a modified or intermittent fast aimed at weight or appetite, the small number of calories is usually fine and often helpful.
How long should a bone broth fast last?
Most people keep it short, from part of a day to a day or two. Longer fasts of any kind should only be done under professional guidance.
Does a bone broth fast trigger autophagy?
Possibly to a small degree, but likely less than a true water fast, because broth provides calories and protein. Most autophagy evidence is from animal studies, and human evidence is preliminary.
Is a bone broth fast safe?
For many healthy adults a short one is generally well tolerated, and broth makes it more comfortable than water alone. It is not safe during pregnancy or nursing, for anyone with a history of disordered eating, or without care for people with diabetes or a medical condition.
What can I have on a bone broth fast?
Bone broth, water, and unsweetened tea or coffee. The broth provides warmth, sodium, and a little protein, which is what makes the fast far more comfortable than water alone.
What are the benefits of a bone broth fast?
Mostly the general benefits of a gentle fast, a possible appetite reset and the metabolic switch toward fat-burning, made more comfortable by broth’s warmth, sodium, and protein. The evidence is promising but short-term, so keep expectations grounded.
Sources & References
Independent, third-party sources. No brand-funded or competitor-commissioned studies are cited as evidence; where cited research was industry-funded, that is noted in the text.
[1] Petrucci K. Dr. Kellyann’s Bone Broth Diet (New York Times bestseller). Rodale, 2015; reviewed in Publishers Weekly. www.publishersweekly.com/978-1-62336-671-1
[2] “Research on intermittent fasting shows health benefits.” National Institute on Aging, U.S. National Institutes of Health. www.nia.nih.gov/news/research-intermittent-fasting-shows-health-benefits
[3] de Cabo R, Mattson MP. “Effects of Intermittent Fasting on Health, Aging, and Disease.” New England Journal of Medicine, 2019. pubmed.ncbi.nlm.nih.gov/31881139/
[4] “Bone Broth: Is It Good for You?” (L.J. Amaral, RD). Cedars-Sinai. www.cedars-sinai.org/stories-and-insights/expert-advice/bone-broth
[5] Alcock RD, Shaw GC, Burke LM. “Bone Broth Unlikely to Provide Reliable Concentrations of Collagen Precursors.” Int. J. Sport Nutrition & Exercise Metabolism, 2019. doi.org/10.1123/ijsnem.2018-0139