Does Bone Broth Break a Fast? It Depends on the Goal

Does Bone Broth Break a Fast? It Depends on the Goal

A cup of bone broth has 35 to 50 calories and 8 to 10 grams of protein, depending on the brand. By any strict definition, that breaks a fast. But "breaking a fast" means different things to someone counting calories on 16:8, someone fasting for autophagy, and someone prepping for a blood draw. The real answer is goal-specific.

Key Takeaways

• Bone broth contains calories and protein. It ends a zero-calorie fast.
• For weight loss, a single cup is unlikely to matter. For autophagy, the amino acids are the problem, not the calories.
• Before a fasting blood test or during a religious fast, bone broth is not allowed. Only plain water is.
• There is no evidence-based "50-calorie rule" that keeps you in a fasted state.

Does Bone Broth Break a Fast? The Answer by Fasting Goal

The question collapses once you define the goal. Here is the breakdown.

What Is Actually in a Cup of Bone Broth?

The "bone broth won't break your fast" claim usually comes from brands selling broth. Their own labels tell a different story:

Source: brand product pages, accessed September 2026. Homemade broth varies and has no standardized label.

Every option delivers real protein and real calories. The Swanson label notes "not a good source of protein," which is true for a meal but irrelevant for a fast, where any protein matters.

Does Bone Broth Break Intermittent Fasting for Weight Loss?

For a 16:8 or OMAD plan aimed at calorie control, a cup of bone broth is 35 to 50 calories. That is roughly 2% of a typical daily intake. It will not undo a caloric deficit.

Some context: in a year-long randomized trial of 100 metabolically healthy adults with obesity, the alternate-day fasting group ate 25% of their energy needs on fast days and still matched the weight loss of a daily calorie-restriction group (Trepanowski et al. 2017, JAMA Internal Medicine). Research "fasts" often include some calories.

A single cup is not three to six cups. The Kettle & Fire bone broth diet recommends three to six cups on fast days. That is 105 to 300 calories and 24 to 60 grams of protein, a very low calorie diet, not a fast.

Does Bone Broth Kick You Out of Ketosis?

Probably not. A cup of bone broth has 2 grams of carbohydrate or less. The metabolic switch to fatty acid and ketone oxidation typically happens between 12 and 36 hours without food, depending on liver glycogen stores at the start (Anton et al. 2018, Obesity). A near-zero-carb cup of broth is unlikely to reverse that switch.

Protein is a separate question. Large protein loads can stimulate insulin enough to blunt ketone production, but a single 8 to 10 gram serving is a small dose. If you are fasting for ketones and mental clarity, one cup is probably fine. Five cups is a different conversation.

Does Bone Broth Stop Autophagy?

This is where the calories-only framing falls apart. Autophagy, the cellular recycling process linked to longevity research, is induced by food deprivation. A 2018 review in Ageing Research Reviews concluded that fasting upregulates autophagy across a wide variety of tissues, though most of the underlying evidence comes from animal and cell studies, not human trials.

The signals that suppress autophagy are amino acids and insulin. Bone broth is essentially dissolved protein: 8 to 10 grams of amino acids per cup, rich in glycine from gelatin. In a small study of nine healthy subjects, glycine alone produced a slight insulin elevation (Gannon et al. 2002, American Journal of Clinical Nutrition).

No human study has measured autophagy directly after consuming bone broth. Bone broth likely interrupts autophagy because it delivers exactly the nutrient signal (amino acids) that autophagy responds to. "Likely" because autophagy cannot be measured at home and the dose-response curve in humans is not established. If autophagy is your goal, broth during the fasting window is the wrong move.

Can You Have Bone Broth Before a Fasting Blood Test or During a Religious Fast?

No. MedlinePlus states you should not eat or drink anything except plain water for 8 to 12 hours before a fasting blood test. No juice, no coffee, no gum, no broth. Follow your clinician's instructions for any test or procedure.

Religious fasts follow each tradition's own rules. Broth is food in all of them.

What About a "Bone Broth Fast"?

Kettle & Fire's protocol calls it a fast: five to eight cups of bone broth, plus herbal tea and water, over 24 hours. The brand claims this supports the body's "natural healing processes without taking you out of a fasted state." That claim is not supported by any cited human study on the page.

The label math: five to eight cups at 35 to 50 calories is 175 to 400 calories and 40 to 80 grams of protein per day. Five cups of a 350 mg sodium broth is 1,750 mg of sodium. That is a very low calorie liquid diet, not a fast. Some people find it more tolerable than water-only fasting. Calling it a "fast" is a stretch.

People with kidney disease, heart failure, high blood pressure, diabetes managed with medication, a history of eating disorders, or who are pregnant or under 18 should talk to a clinician before any extended fast or very low calorie diet.

What Can You Drink That Will Not Break a Fast?

For a strict zero-calorie fast, the short list: water, plain sparkling water, black coffee, and plain tea. For longer fasts, sugar-free electrolytes help with sodium and potassium. Lemon water is borderline (minimal calories, but check the goal table above).

A caffeine pouch like Roon sits between the lip and gum and is not swallowed as food. It contains zero calories and zero sugar but does contain sucralose, and the evidence on sucralose and insulin is mixed. For water-only, blood test, or religious fasts, it is excluded the same way broth is.

You can also read about supplements, creatine, and vitamins while fasting.

Conclusion

Whether bone broth breaks your fast depends on which fast you are doing. For weight loss, one cup barely moves the needle. For autophagy, the amino acids are the issue, and broth delivers them directly. For a blood test or religious fast, it is off the table. There is no universal "50-calorie rule" backed by evidence. Define the goal, then decide.

Frequently Asked Questions

Does bone broth break a fast?

Strictly, yes. Commercial bone broth has 35 to 50 calories and 8 to 10 grams of protein per cup. Whether it matters depends on the goal: negligible for calorie-based weight loss, likely problematic for autophagy, and not allowed before a fasting blood test.

How many calories break a fast?

There is no evidence-based calorie threshold. The popular "50-calorie rule" and "10-calorie rule" circulate online, but neither is supported by a published study. The better question is which metabolic signal your fast is trying to avoid: calories, insulin, amino acids, or all food.

Does chicken broth or bouillon break a fast?

Yes. Regular chicken broth has fewer calories (about 10 per cup for Swanson chicken broth) but still contains protein and sodium. Bouillon cubes dissolved in water have similar profiles. Neither is plain water.

Does bone broth spike insulin?

No human study has measured the insulin response to bone broth specifically. A 2002 study found that glycine, the dominant amino acid in gelatin, slightly raised serum insulin in nine healthy subjects. A slight rise is not a spike, but it is not zero.

Can I drink bone broth during a 72-hour fast?

If you add bone broth, you are doing a very low calorie liquid diet, not a 72-hour fast. That distinction matters for autophagy, gut rest, and any research protocol. Some people choose broth for comfort and sodium during long fasts. Be clear about what you are actually doing.

When is the best time to drink bone broth when fasting?

The first thing in your eating window. That way you get the sodium, protein, and warmth without interrupting the fasting hours you have already completed.

For the Fasting Hours When Broth Is Off the Table

People reach for bone broth mid-fast because the hours drag and energy dips. The label math above shows broth is food, 35 to 50 calories and 8 to 10 grams of protein, so it does not solve the energy problem without ending the fast.

Roon is a zero-nicotine, zero-sugar, zero-calorie oral pouch (Cool Mint, 15 per tin) with 80 mg caffeine, 60 mg L-theanine, 25 mg methylliberine (Dynamine), and 5 mg theacrine (TeaCrine). It sits between your lip and gum. Nothing is swallowed. In a randomized, double-blind, crossover PK study (n=12), methylliberine slowed caffeine's oral clearance from 41.9 to 17.1 L/hr and extended its half-life from 7.2 to 15 hours with no increase in peak concentration (Mondal et al. 2022). That study used 100 mg methylliberine + 150 mg caffeine, roughly 4x and 1.9x Roon's doses, so the effect at 25 mg + 80 mg is directionally the same, not identical. The felt window is 6 to 8 hours, enough to cover most of a 16:8 fasting block. Stop at least 8 hours before bed.

The caveat: Roon contains sucralose, and the evidence on sucralose and insulin is mixed. A water-only, blood test, or religious fast excludes it just as it excludes broth. From $9.16 per tin on the 12-tin subscription ($0.61 per pouch), or $15.00 per tin one-time, with a 30-day money-back guarantee on your first order. Try Roon.

Related from Roon

• Do Roon Pouches Break a Fast?
• Does Coffee Break a Fast?
• Does Sucralose Break a Fast?
• Intermittent Fasting and Focus: The Ketone Connection

Written by Roon Team