Does Bone Broth Break a Fast?

Bone broth occupies a unique position in the fasting world. It contains calories and protein, which technically means it breaks a fast. Yet many experienced fasters, doctors, and fasting protocols not only permit bone broth during fasting but actively recommend it.

So what is the truth? Does bone broth break a fast, and does it matter?

Quick Answer: Technically, yes -- bone broth breaks a strict fast. A cup contains approximately 30 to 50 calories and 5 to 10 grams of protein, which will trigger some metabolic response. However, many fasting protocols accept bone broth because its benefits (electrolytes, gut support, sustainability) outweigh the minor caloric impact. For standard 16:8 fasting, save it for your eating window. For extended fasts of 24+ hours, bone broth can be a valuable tool to help you complete the fast successfully.

What Is in Bone Broth?

Understanding why bone broth is controversial requires knowing what it contains. A typical cup (240 ml) of homemade bone broth provides:

Calories: 30 to 50
Protein: 5 to 10 grams (primarily collagen and gelatin)
Fat: 1 to 3 grams
Carbohydrates: 0 to 1 gram
Sodium: 300 to 500 mg
Potassium: 200 to 400 mg
Magnesium: 10 to 20 mg
Calcium: 10 to 30 mg
Glycine: 1 to 3 grams
Proline: 1 to 2 grams

The protein content is what makes bone broth different from other fasting beverages like black coffee or tea. Amino acids, particularly leucine and other branched-chain amino acids, can stimulate insulin and mTOR pathways. However, collagen-derived amino acids in bone broth have a very different profile than whey or meat protein -- they are low in leucine and high in glycine and proline, which are less insulinogenic.

The Strict vs. Practical Fasting Debate

The Strict View

If you define fasting as consuming zero calories, then bone broth breaks your fast. Period. The protein and calories in bone broth will trigger some degree of digestive activity, insulin secretion, and mTOR activation. For people fasting specifically to maximize autophagy, even the modest protein content of bone broth may reduce autophagic activity.

Under the strict definition, you should save bone broth for your eating window or use it to break your fast when your fasting period ends.

The Practical View

Many physicians and fasting experts take a more pragmatic approach. Dr. Jason Fung, one of the most published researchers on fasting, permits bone broth during extended fasts. His reasoning: the small caloric impact is vastly outweighed by the practical benefits of making the fast sustainable.

The practical view holds that a 36-hour fast completed with two cups of bone broth delivers far more benefits than a 36-hour fast that you abandon at hour 20 because you felt terrible.

This pragmatic approach makes sense. The metabolic benefits of fasting -- fat burning, insulin reduction, cellular repair -- are primarily driven by the extended absence of significant caloric intake, not by absolute zero-calorie purity.

When Bone Broth Makes Sense During Fasting

Extended Fasts (24+ Hours)

For 36-hour fasts and multi-day fasting protocols, bone broth serves multiple critical functions:

Electrolyte replacement. Bone broth is a natural source of sodium, potassium, and magnesium -- the three electrolytes most depleted during fasting. This can prevent headaches, dizziness, and muscle cramps.

Gut lining support. The glycine and glutamine in bone broth support intestinal integrity. During extended fasts, maintaining gut lining health helps prevent issues when you eventually reintroduce food.

Psychological sustainability. Having something warm and savory to consume during a long fast provides comfort and helps you complete the full fasting period. Completing a 36-hour fast with bone broth is better than breaking at 18 hours.

Transition Fasts

If you are new to fasting and working up to longer windows, bone broth can serve as a stepping stone. Start with a "bone broth fast" where you consume only water, tea, coffee, and bone broth for 24 hours. This gives you the experience of extended fasting with a safety net.

Gut Health Protocols

Some fasting protocols specifically focus on gut health and healing. In these contexts, bone broth is not a compromise -- it is part of the protocol. The collagen, gelatin, glycine, and glutamine in bone broth actively support gut repair, complementing the gut health benefits of fasting itself.

When to Avoid Bone Broth During Fasting

Standard 16:8 or 18:6 Fasting

If you are doing a standard intermittent fasting schedule, you do not need bone broth during your fasting window. Your fast is short enough that electrolyte needs can be met with salt water, and you have an eating window where bone broth can be consumed as a nutritious food.

Save bone broth for breaking your fast or as part of your eating window meals.

Strict Autophagy Fasting

If your primary goal is maximizing autophagy, avoid bone broth during your fast. The amino acids, particularly glycine, may modulate autophagic pathways. Stick to water, black coffee, and plain tea for autophagy-focused fasting.

Calorie-Counting Protocols

If you are tracking calories precisely for weight loss, be aware that bone broth is not calorie-free. Two to three cups throughout a fasting day adds 60 to 150 calories. While this is unlikely to derail weight loss, it should be accounted for in your overall caloric tracking.

How to Use Bone Broth Strategically

During Extended Fasts

Consume 1 to 3 cups of bone broth spread throughout the day. Sip slowly rather than drinking a full cup at once. Add a pinch of salt if the broth is not already well-seasoned.

Morning: A cup of bone broth instead of or alongside your morning coffee.

Midday: A cup when hunger or fatigue peaks, typically 18 to 24 hours into the fast.

Evening: A cup before bed to support sleep and provide minerals for overnight recovery.

As a Fast-Breaking Food

Bone broth is arguably the best food to break an extended fast. It is warm, liquid, easily digestible, and provides minerals and amino acids without overwhelming your dormant digestive system. Drink a cup of bone broth 15 to 30 minutes before your full meal to ease the transition.

Making vs. Buying

Homemade bone broth is superior in nutrient content and allows you to control sodium levels. Simmer beef or chicken bones with water, apple cider vinegar (to extract minerals), and salt for 12 to 24 hours.

Store-bought bone broth varies widely in quality. Look for brands with at least 8 grams of protein per cup, no added sugars, and minimal additives. Many commercial "bone broths" are glorified stock with lower nutritional content.

Check labels carefully. Some products marketed as bone broth contain yeast extract, sugar, or other ingredients that add unnecessary calories and may include components you want to avoid during fasting. For more on what breaks a fast, including hidden ingredients in common foods, see our complete guide.

Bone Broth vs. Regular Broth vs. Stock

These terms are often used interchangeably, but they differ:

Bone broth: Made from bones simmered for 12 to 48 hours. Higher in collagen, gelatin, minerals, and amino acids. Thicker when cooled. This is what you want for fasting.

Stock: Made from bones simmered for 4 to 6 hours. Less concentrated but still nutritious. Acceptable substitute.

Broth: Made from meat (not bones) simmered for 1 to 2 hours. Lower in collagen and minerals. Not as beneficial for fasting purposes.

For fasting, always choose bone broth or stock over regular broth.

Bone Broth and Specific Fasting Methods

16:8 fasting: Save bone broth for your eating window. No need during a 16-hour fast.

20:4 / OMAD: Bone broth during the fasting window is optional but can help with hunger management. Use it if needed.

24-hour fasts: A cup or two of bone broth can make the fast much more manageable, especially for beginners.

36-hour fasts: Bone broth is highly recommended. Extended fasts benefit significantly from the electrolyte and amino acid support bone broth provides.

Multi-day fasts (48+ hours): Bone broth becomes an important tool for safety and sustainability. Consult a healthcare provider for fasts of this length.

5:2 diet: On low-calorie days (500 to 600 calories), bone broth can be a valuable low-calorie, nutrient-rich option that helps you stay within your limit while getting essential nutrients.

How Fasted Helps

Fasted tracks your fasting duration and helps you plan when to incorporate bone broth into your routine. For extended fasts, the timer shows your progress and can remind you to sip bone broth at regular intervals. The meal logging feature lets you track bone broth consumption to ensure you are staying within your protocol's guidelines.

Frequently Asked Questions

How many calories does bone broth have?

Homemade bone broth typically contains 30 to 50 calories per cup. Store-bought varieties range from 10 to 50 calories depending on concentration and brand. Always check the nutrition label on commercial products.

Can I add anything to bone broth while fasting?

Salt is fine and recommended. A small amount of apple cider vinegar, turmeric, ginger, or black pepper adds negligible calories and can enhance the nutritional value. Avoid adding butter, cream, noodles, or vegetables, as these significantly increase caloric content.

Is bone broth better than electrolyte supplements during fasting?

Both serve the electrolyte function. Bone broth provides additional benefits (collagen, amino acids, gut support) that pure electrolyte supplements do not. However, bone broth also contains protein and calories that electrolyte supplements do not. For strict fasting, use electrolyte supplements. For extended or flexible fasting, bone broth is the superior choice.

Can vegetarians use anything similar to bone broth during fasting?

Vegetable broth is lower in protein and collagen but can still provide minerals and warmth during extended fasts. Miso broth is another option with minimal calories and good sodium content. Neither provides the collagen benefits of bone broth, but both can help with fast sustainability.

Will bone broth spike my blood sugar?

No. Bone broth contains virtually no carbohydrates. The small amount of protein will trigger a minimal insulin response, but it will not spike blood sugar. For most people, the glycemic impact of bone broth is negligible.