Bone Broth and Intermittent Fasting: UK Guide

Bone broth and intermittent fasting are increasingly combined by people seeking to manage hunger, support hydration, and maintain electrolyte balance during fasting periods. Bone broth is a protein-rich liquid made by simmering animal bones for 12 to 24 hours, yielding collagen-derived amino acids, minerals, and small amounts of fat. Whether it is compatible with a fast depends on the type of fasting being followed and the individual's health goals. This article explores the nutritional profile of bone broth, its potential benefits and risks alongside intermittent fasting, and what UK guidance says about this dietary approach.

Does bone broth break a fast?

Bone broth technically breaks a strict caloric fast as it contains calories and protein, but its practical impact depends on the fasting goal, such as metabolic health, autophagy, or clinical preparation.

Whether bone broth breaks a fast depends on the fasting goal, because a plain, unseasoned bone broth contains calories and macronutrients that technically end a strict caloric fast. Bone broth is made by simmering animal bones and connective tissue for an extended period, typically 12 to 24 hours, producing a liquid rich in protein, collagen-derived amino acids, and small amounts of fat. Nutritional composition varies considerably depending on the bones used, cooking duration, and whether vegetables or seasoning are added; a typical 240 ml serving of plain bone broth may provide roughly 30 to 50 kilocalories and 6 to 10 grams of protein, though figures across UK commercial products and homemade preparations differ widely and checking individual product labels is advisable.^[9]

The practical impact of consuming bone broth during a fast depends on the type of fast being followed. Even a modest protein and calorie intake can stimulate an insulin response, though the magnitude of this effect from a small serving of broth has not been well characterised in human studies and should be regarded as uncertain. For those practising time-restricted eating primarily for metabolic or weight management reasons, a small serving of plain bone broth is often considered a minimal disruption. For those pursuing a strict water-only fast, or fasting for specific clinical purposes such as pre-operative preparation or certain gut investigations, any caloric intake would generally be inappropriate; individuals should follow the specific written guidance provided by their hospital team or clinical team for their procedure, as requirements vary.

For autophagy-focused fasting, the picture is more nuanced. Amino acids, particularly leucine and glutamine found in bone broth, may stimulate the mTOR pathway and potentially reduce autophagic activity.^[4][5] This is a plausible mechanism supported by cell and animal research, but the precise threshold at which this occurs in humans, and whether the quantities present in a small serving of broth are sufficient to have a meaningful effect, is not yet clearly established in the published literature. Individuals should consider their specific fasting objective before incorporating bone broth into their fasting window, and those with medical conditions should seek guidance from their GP before making changes to their dietary pattern.

What are the health benefits of combining bone broth with intermittent fasting?

Combining bone broth with intermittent fasting may help manage hunger and support electrolyte balance, though robust clinical evidence specific to this combination is currently lacking.

Combining bone broth with intermittent fasting may offer practical advantages in managing hunger, electrolyte balance, and dietary adherence, though robust clinical evidence specific to this combination is lacking. Intermittent fasting, in its various forms including the 16:8 method and the 5:2 approach, has been studied in observational and controlled trials with some evidence of improvements in body weight and metabolic markers; however, systematic reviews comparing intermittent fasting with continuous calorie restriction have found mixed results, and outcomes vary considerably between individuals.^[6][7] Bone broth, consumed during or around the eating window, may complement a fasting approach through its nutritional composition, though direct evidence for a synergistic effect is not available.

One of the most commonly reported practical benefits is appetite management. The protein content of bone broth, primarily in the form of gelatin and collagen peptides, may promote satiety by influencing gastric emptying and gut hormones involved in hunger signalling.^[1] Human evidence for this specific effect from bone broth is limited, and this should be regarded as a plausible practical benefit rather than an established clinical finding.

Bone broth also provides electrolytes, including sodium, potassium, and magnesium, which may be relevant during extended fasting periods, particularly in those who are physically active. The extent of electrolyte depletion during fasting varies by duration, fluid intake, and individual factors, and most people following short-duration intermittent fasting do not require supplementation beyond adequate hydration. Unsupervised high-dose electrolyte supplementation is not recommended. The glycine content of bone broth has been associated in some studies with benefits for sleep quality and gut lining integrity, though much of this evidence comes from animal studies or small human trials and should be interpreted cautiously.^[3][19]

These potential benefits are best realised when bone broth is part of a balanced, nutrient-sufficient eating pattern overall. The British Dietetic Association (BDA) provides patient-friendly guidance on intermittent fasting approaches that may be a useful starting point for those considering this dietary pattern.

Nutritional Profile of Bone Broth and Its Role During a Fast

Bone broth provides roughly 30 to 50 kilocalories and 6 to 10 grams of protein per 240 ml serving, with variable electrolytes, but is not a complete protein source and values differ widely between products.

Bone broth provides a distinct nutritional profile that sets it apart from plain water or herbal teas commonly consumed during fasting periods. Nutritional composition varies considerably depending on the bones used, cooking duration, and whether vegetables or seasoning are added. A typical 240 ml serving of homemade or commercially prepared bone broth may contain approximately 30 to 50 kilocalories and 6 to 10 grams of protein, with small quantities of fat; however, these figures are indicative only and checking individual product labels is strongly recommended, as values across UK brands and homemade preparations differ widely.^[9]

The protein in bone broth is predominantly derived from collagen, which breaks down during prolonged simmering into gelatin and individual amino acids including glycine, proline, and hydroxyproline.^[9] Bone broth is not a complete protein source, as it is low in certain essential amino acids, notably tryptophan, and should not be relied upon as a primary protein source.^[9] Those requiring adequate protein intake should ensure this is met through a varied diet during their eating window.

In terms of micronutrients, bone broth contains variable amounts of calcium, phosphorus, magnesium, and potassium, though the quantities are generally modest and depend heavily on preparation method. Many commercially available bone broths are high in sodium; individuals managing blood pressure, kidney disease, or heart failure should check labels carefully and consider low-sodium varieties or homemade preparations where sodium can be controlled. Checking allergen information on product labels is also advisable.

Individuals with gout or hyperuricaemia should be aware that bone broth may contain purines, which can contribute to uric acid levels; personalised advice from a GP or registered dietitian is recommended in this group.

During a fasting period, bone broth can serve a practical role in maintaining hydration and providing a small amount of electrolytes without the caloric load of a full meal. For those consuming it within their eating window, it can contribute to overall protein intake and support dietary variety as part of a balanced diet.

Are there any risks or side effects of bone broth during intermittent fasting?

Key risks include high sodium content in commercial broths, potential purine intake for those with gout, and hypoglycaemia risk for people with diabetes taking certain medications who fast without medical supervision.

Bone broth is generally well tolerated, but there are several considerations worth noting when combining it with intermittent fasting. One concern relates to sodium content. Many commercially prepared bone broths contain high levels of added salt, and consuming these regularly, particularly during a fasting period when overall food intake is reduced, could contribute disproportionately to daily sodium intake. Individuals with hypertension, kidney disease, or heart failure should check labels carefully and opt for low-sodium varieties or homemade preparations where sodium can be controlled.

Lead contamination has been raised as a potential concern in some published analyses of bone broth, as heavy metals can leach from bones during prolonged cooking.^[2] The Food Standards Agency (FSA) provides guidance on heavy metals in food and is the appropriate body for food safety concerns of this nature.^[10] While the quantities detected in most studies have been low, individuals who consume bone broth very frequently, particularly those who are pregnant or breastfeeding, may wish to vary their protein sources and not rely solely on bone broth.

People with type 1 diabetes, or those taking insulin, sulfonylureas, or SGLT2 inhibitors, face a particular risk of hypoglycaemia or other complications when fasting and should not undertake intermittent fasting without prior discussion with their diabetes care team or GP.^[11][12] Diabetes UK provides specific guidance on fasting with diabetes that is a useful starting point for this group.

Individuals with gout or hyperuricaemia should be aware that bone broth may contain purines and should seek personalised advice before consuming it regularly.

For those following intermittent fasting for specific medical reasons, such as managing blood glucose in type 2 diabetes or preparing for a clinical procedure, it is important to clarify with a GP or dietitian whether any caloric intake during the fasting window is appropriate.

Side effects of intermittent fasting itself, including headaches, dizziness, irritability, and difficulty concentrating, are common during the adaptation phase. If symptoms are severe or persistent, or if someone experiences fainting, confusion, or persistent vomiting, they should stop the fast and contact their GP or call NHS 111. Suspected adverse reactions to a medicine or medical device can be reported to the MHRA via the Yellow Card scheme. Concerns about food safety, including suspected contamination of a food product, should be reported to the local authority environmental health team or the FSA.

What do NHS and UK nutrition guidelines say about intermittent fasting?

The NHS acknowledges intermittent fasting as one weight management approach but does not endorse it as a first-line strategy, and NICE recommends any dietary intervention be sustainable and professionally supported.

The NHS acknowledges intermittent fasting as one approach to weight management but does not currently endorse it as a first-line dietary strategy for the general population. NHS guidance on healthy eating is based on the Eatwell Guide, which recommends proportionate intake of starchy carbohydrates, fruits and vegetables, proteins, and dairy or dairy alternatives, with limited saturated fat, salt, and free sugars.^[13][14] Intermittent fasting is not explicitly featured in the Eatwell Guide framework.

NICE guidance on obesity management recommends a range of dietary approaches for weight loss, including calorie-deficit diets, and acknowledges that different approaches suit different individuals.^[15][16] NICE emphasises that any dietary intervention should be sustainable, nutritionally adequate, and ideally supported by a healthcare professional, particularly for individuals with existing health conditions. Readers should consult the current NICE obesity management guideline directly for the most up-to-date recommendations, as guidance is subject to revision.

For individuals considering intermittent fasting alongside bone broth or other dietary modifications, a GP or registered dietitian is the most appropriate first point of contact, particularly for those with diabetes, cardiovascular disease, a history of disordered eating, or those who are pregnant or breastfeeding. Registered dietitians in the UK are regulated by the Health and Care Professions Council (HCPC), and their registration can be verified via the HCPC online register.^[17][18] The BDA also publishes patient-facing food fact sheets on intermittent fasting that provide a UK-specific evidence summary.

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, for those exploring clinically supervised options alongside lifestyle changes such as dietary modification. Overall, the evidence base for intermittent fasting continues to grow, but individuals are encouraged to seek personalised advice rather than applying population-level findings to their own health context.

Scientific References

1. Oral ingestion of a hydrolyzed gelatin meal in subjects with normal weight and in obese patients.
2. The risk of lead contamination in bone broth diets.
3. Analysis of the Anti-Inflammatory Capacity of Bone Broth in a Murine Model of Ulcerative Colitis.
4. Regulation of autophagy by amino acids and MTOR-dependent signal transduction.
5. Bidirectional transport of amino acids regulates mTOR and autophagy.
6. Intermittent Fasting versus Continuous Calorie Restriction.
7. The impact of intermittent fasting on body composition and cardiometabolic outcomes in overweight and obese adults: a systematic review and meta-analysis of randomized controlled trials.
8. Intermittent fasting for adults with overweight or obesity (Cochrane Database of Systematic Reviews).
9. Physicochemical and Functional Properties of Yanbian Cattle Bone Gelatin Extracted Using Acid, Alkaline, and Enzymatic Hydrolysis Methods.
10. Food Standards Agency — food safety and food hygiene guidance.
11. Type 2 diabetes — Treatment summaries (BNF/NICE).
12. Is Time-Restricted Eating Safe in the Treatment of Type 2 Diabetes? — A Review of Intervention Studies.
13. The Eatwell Guide.
14. The Eatwell Guide (policy document).
15. Overweight and obesity management (NG246).
16. Overweight and obesity management (NG246) — Physical activity and diet chapter.
17. Dietitian registration — Health and Care Professions Council (HCPC).
18. Check HCPC registration — British Dietetic Association.
19. Bone Broth Benefits: How Its Nutrients Fortify Gut Barrier in Inflammatory Bowel Disease.

Frequently Asked Questions