Bone broth fasting: what it really changes

Bone broth fasting means replacing meals with a salted broth, made from vegetables or bones, for several consecutive days. It is presented as a fast, but as soon as a salted liquid other than water enters the day, the practice has already left strict fasting for what medicine calls a modified fast.

This is the thesis this article defends: that shift is not a detail of vocabulary. Salt and the warmth of the liquid genuinely act on the sensation of hunger, which makes the practice more bearable than a water-only fast – but nutritional intake itself stays very low across the whole day. Feeling less hungry does not mean the body’s needs are being met.

Here you will find what broth genuinely changes about hunger, what its sodium content amounts to over a day of cleansing – without a single figure or dose – what distinguishes vegetable broth, bone broth and an industrial stock cube, and what a return to ordinary eating involves medically after several days of the practice. This page details no protocol to follow alone.

What is bone broth fasting?

Bone broth fasting means replacing every meal with a liquid, strained broth – with no solid pieces – for several consecutive days, sometimes supplemented with water. This broth can be prepared from vegetables, from bones, or reconstituted from an industrial cube dissolved in hot water.

Strictly defined, a fast is limited to water. As soon as a salted broth is added, this is no longer a strict fast but a modified fast: a separate category, which keeps a small intake of calories, sodium and, depending on the type of broth, protein. This is not a nuance of vocabulary: it is what shapes the rest of this article.

How does it work?

Two distinct mechanisms are at work in bone broth fasting, and it helps not to confuse them. The first concerns hunger: a hot liquid slows stomach emptying and prolongs the sensation of gastric fullness, while salt contributes to the satisfaction felt at the moment of drinking it. Both effects make the practice more bearable day to day than a water-only fast, without covering the day’s nutritional needs.

The second mechanism concerns actual intake: whether it is vegetable broth, bone broth or an industrial cube, calorie and protein content stays very low across a full day. The body finds itself, on this front, in a situation close to a strict fast: glycogen reserves gradually empty, and the body turns to its fat, and, without sufficient protein, to its muscle reserves.

Vegetable broth, bone broth, industrial stock cube

Bone broth fasting does not come in separately named methods; it is the type of broth used that varies, and that variation changes what the practice genuinely delivers. Vegetable broth, made by long cooking of vegetables in water and then straining, mainly supplies water, salt and dissolved minerals, with a protein content close to zero.

Bone broth, prepared from bones and sometimes cartilage cooked at length, contains a little gelatine and collagen, giving it a slightly higher protein content than vegetable broth – without that being enough to cover a day’s needs. An industrial stock cube dissolved in water, finally, mainly supplies salt, flavourings and sometimes flavour enhancers, with a near-zero intake from real ingredients: it is not the equivalent of broth made from fresh ingredients, even if the perceived salty taste can be similar.

Potential benefits of bone broth fasting

Several benefits circulate around bone broth fasting, particularly around bone broth itself, presented in some places as good for joints or the gut. The table below summarises what can reasonably be expected, with the associated evidence level: caution requires a deliberately strict rating on this subject.

Effect on weight loss

Weight loss during bone broth fasting mainly comes from the sharp reduction in calorie intake compared with an ordinary diet – not from any particular property of the broth itself. This effect is real, but it stays variable depending on what follows it: hunger blunted during the cleanse can translate into more generous intake once the practice ends.

One point is worth noting: a high sodium intake can promote water retention in some people, which can mask part of the expected weight loss or, conversely, give an impression of rapid loss that is in fact only water. To set a realistic, lasting weight goal, our calorie and basal metabolic rate calculator remains a better-suited tool than temporarily substituting meals with a salted liquid.

Effect on metabolism

In terms of energy intake, bone broth fasting sits closer to a strict fast than to a simply lightened diet: the calories broth supplies stay minimal, whatever type is chosen. The body therefore adjusts its resting energy expenditure to preserve its reserves, an adaptive mechanism with nothing specific to this particular practice.

Over several days, this mechanism combines with the mobilisation of part of the muscle reserves, for lack of sufficient protein intake – even for a bone broth rich in gelatine. Presenting bone broth fasting as a way to speed up the metabolism is therefore not consistent with what is understood of how it actually functions.

Effect on autophagy

Another argument frequently raised around fasting: autophagy, that cell-recycling mechanism. It is not measured in practice in humans under bone broth fasting. The very low calorie intake of this practice brings it closer, on this front, to a strict fast than to a simple calorie restriction – but nothing allows the claim that a precise threshold is crossed at a given duration.

The salt and warmth of the broth, which explain most of the comfort felt during the practice, have no demonstrated link to this cellular mechanism. Confusing felt comfort with a measurable biological effect is one of the most common traps around this practice.

Effect on blood sugar

A strained broth, with no solid piece, supplies very little carbohydrate, whatever type is chosen. Blood sugar therefore evolves, over the days, in a way fairly close to what happens during a strict fast: a gradual decline followed by stabilisation at a low level, with fatigue and difficulty concentrating possible in some people.

In someone with diabetes on treatment, this decline can interact directly with ongoing treatment and expose them to a risk of low blood sugar: the fact that the practice keeps a sodium intake changes nothing about that risk, which depends on carbohydrate intake, almost nil in a broth.

Effect on insulin

Because a broth’s carbohydrate content is very low, insulin secretion stays low during the practice, a pattern close to what is observed during a strict fast. This is not an effect specific to broth: it is the direct consequence of a much-reduced calorie and carbohydrate intake, whatever form it takes.

The fact that broth keeps a minimal calorie intake changes nothing for someone whose treatment acts on insulin secretion or action: this prolonged decline deserves prior medical advice, as it would for any practice that sharply restricts intake over several days, near-zero intake or not.

Effect on cholesterol

Data on the specific effect of bone broth fasting on the lipid profile are close to non-existent as such: most available knowledge concerns calorie restriction in general, not this precise practice. Nothing allows attributing to broth itself a standalone effect on cholesterol.

One point is worth noting: some bone broths, prepared from fat-rich bones, can contain more fat than their clear, liquid appearance suggests, depending on preparation. This is not a sought-after or documented beneficial effect: it is a variability worth knowing about.

Effect on muscle mass

This is one of the points where bone broth stands out most clearly from vegetable broth or an industrial cube: its gelatine content gives it a slightly higher protein intake, though it still stays, in every case, far below a full day’s needs. Gelatine, on top of that, does not have the same amino acid profile as a complete protein source.

Over several consecutive days, this insufficient protein intake – whatever broth is chosen – can push the body to mobilise part of its muscle reserves to meet its amino acid needs. This is a point of vigilance made more important by the fact that the hunger blunted by broth can encourage extending the practice beyond what someone would do with water alone.

What the research says

Data built specifically around bone broth fasting remain rare in humans. Available knowledge covers, separately, severe calorie restriction, the effect of sodium on blood pressure, or the nutritional composition of broths – rarely the particular combination that a multi-day broth cleanse represents.

This point is not settled, and it is better to say so plainly: the claims circulating around bone broth, particularly regarding joints and the gut, go considerably further than what currently available data can support. What can be stated with more confidence concerns mechanisms established separately: very low calorie intake, cumulative sodium intake, and the effect of a hot liquid on the sensation of hunger.

The risks of bone broth fasting

The first risk, the most specific to this practice, concerns sodium. A broth is, by nature, a salted liquid; repeating several bowls in a single day, then across several consecutive days, makes that intake add up, often well beyond what someone intuitively perceives. This page gives no figure on the matter, but the principle is worth knowing: a high, repeated sodium intake can promote water retention and put pressure on blood pressure, particularly in someone with high blood pressure, heart failure, kidney impairment, or on a diuretic.

The second risk lies in the gap already mentioned between comfort and actual intake: because hunger is blunted, some people extend the practice longer than they would with water alone, which deepens the shortfall in protein, fibre and most vitamins over a longer stretch than originally planned.

A third risk concerns industrial cubes specifically: some contain additives, flavourings or flavour enhancers whose tolerance varies from person to person, adding to the sodium already present. Homemade broth does not remove the overall nutritional risks of the practice, but it at least avoids this additional source.

Finally, a less often named risk concerns the sense of safety the practice creates: because it feels gentle, warm and comforting, it can give a false impression of harmlessness, when the nutritional shortfall accumulated over several days remains, in many respects, comparable to that of a strict fast.

Who should avoid bone broth fasting?

Several profiles, for whom sodium intake or the misleading fullness broth provides poses a particular problem, should avoid this practice without prior medical advice, or avoid it outright:

• minors, whose growing bodies cannot tolerate such a restricted intake;
• pregnant or breastfeeding women, for whom the misleading fullness of broth can mask an energy and protein intake insufficient for the child as well;
• anyone with a history of disordered eating, for whom a prolonged restriction can reactivate an already fragile relationship with food;
• people with diabetes on treatment, exposed to a risk of low blood sugar given the near-zero carbohydrate intake;
• anyone on any medication whose effectiveness or tolerability depends on meals or on sodium balance;
• people with high blood pressure or on a diuretic, for whom cumulative sodium intake can interact directly with the treatment;
• people with kidney, liver or heart impairment, for whom managing sodium and fluids is already more delicate;
• frail older adults, for whom the fullness broth provides can mask a protein shortfall that weighs more heavily on already reduced muscle mass;
• people whose BMI is already low, for whom a diet nearly devoid of calories and protein has no justification;
• athletes in a heavy training phase, whose energy and protein needs sit poorly alongside such a reduced intake.

For anyone followed for a chronic condition affecting the heart, kidneys or blood pressure, our page on the limitations of BMI is a reminder that a single indicator never replaces individualised medical advice, particularly before considering a multi-day dietary restriction.

A broth cleanse, presented as gentle because it eases hunger, is not harmless for someone whose BMI is already low or whose relationship with food remains fragile: the fullness it provides can, on the contrary, delay the moment that fragility is noticed. Our page on being underweight sets out the signs that justify a consultation, often well before the question of a broth cleanse even arises.

How do you start bone broth fasting?

Considering several days of bone broth fasting does not start with choosing a recipe: it starts with talking to a health professional, particularly if you are followed for high blood pressure, a heart or kidney condition, or if you take regular medication. The three levels below do not describe cleanse durations to reach: they describe degrees of preparation and attention brought to the practice.

Beginner

Someone discovering the idea of bone broth fasting starts by checking, with a health professional if they fall into one of the profiles detailed above, that the practice does not interact with their health status or current treatments – sodium being, at this stage, the most important question to raise.

Intermediate

Someone wanting to go further benefits from reviewing their blood pressure and their usual sodium intake with a professional, and from consciously choosing between vegetable broth, bone broth or an industrial cube, aware of the differences detailed earlier in this article.

Advanced

Support from a health professional who follows the person before, during and after the practice, with particular attention to blood pressure and signs of water retention, matches the level of supervision this article considers reasonable. This is not a personal discipline target to reach alone: it is a monitoring framework to build with a professional, particularly around sodium.

A sample programme

What bone broth fasting followed in an attentive framework can look like is generally organised in several phases, described here to explain what serious supervision covers – not as a schedule to reproduce alone, nor as a duration to aim for.

• Assessment phase: checking blood pressure, current treatments and the absence of any contraindication among the profiles detailed above, before any decision.
• Monitored cleanse phase: attention to signs of water retention, fatigue or swelling, with stopping criteria defined in advance rather than decided alone partway through.
• Reintroduction phase: a gradual return to solid food, with attention to sodium balance as much as to protein, precisely because this stage corrects both the nutritional shortfall and the salt intake accumulated during the cleanse.
• Review phase: checking that blood pressure and overall dietary balance have returned to a satisfactory level, judged individually rather than against a schedule fixed in advance.

This sequence describes a logic of supervision, not a recipe to apply yourself: none of these phases, particularly the one concerning sodium, substitutes for an individual assessment of your own situation.

What to drink during a bone broth fast?

Bone broth fasting rests, by definition, on a liquid, strained broth – vegetable, bone, or reconstituted from a cube – usually supplemented with water between servings. This page provides no recipe, no quantity and no frequency of consumption: these vary between people and do not, in themselves, constitute a safety guarantee.

What matters more than the exact recipe is keeping in mind what earlier sections have established: whatever type of broth is chosen, sodium intake adds up with each serving, and felt comfort says nothing about how well nutritional needs are actually being met.

What to eat before a bone broth fast?

The question that matters is not so much “what to eat the day before” as “what margin does my body have against sodium and the misleading fullness of broth.” Before considering a multi-day cleanse, several elements weigh directly on how risky the practice is, particularly anything related to blood pressure.

What to eat after a bone broth fast?

This page deliberately sets no quantity, no specific food and no numbered reintroduction schedule, for the same reasons already set out around sodium. After several days of intake that was almost entirely liquid and salty, a gradual return is preferable to an abrupt switch to heavy meals, particularly for someone whose starting nutritional or cardiovascular state was already fragile.

What reintroduction involves around sodium and fullness is summarised in the table below: it describes what deserves gradual attention, not a list of foods to follow.

After a broth cleanse, the question that remains is less “what to eat” than “what reference point to return to”: our ideal weight page builds that reference around a personal goal, rather than a temporary substitution of meals with a salted liquid.

Common mistakes with bone broth fasting

1. Believing a salted broth equals a strict fast: as soon as a salted liquid replaces water alone, the practice changes category and medical name.
2. Multiplying bowls of broth through the day, assuming “liquid means neutral”: each bowl adds sodium, which builds up across the day.
3. Using industrial cubes assuming they equal homemade broth: their nutritional make-up and additives differ clearly from broth made with fresh ingredients.
4. Overlooking cumulative sodium intake across several days of cleansing: this is the most specific point of this practice, and the least often accounted for.
5. Believing bone broth repairs joints or the gut: this claim goes beyond what currently available data can support.
6. Extending the practice because hunger feels less present: felt comfort says nothing about whether protein and calorie needs are being met.
7. Overlooking signs of swelling or water retention: these signs may reflect poorly tolerated sodium intake, particularly in a predisposed person.
8. Practising with unstable high blood pressure without telling a doctor: cumulative sodium intake can interact directly with an ongoing treatment.
9. Confusing vegetable broth and bone broth in terms of protein content: neither covers a full day’s needs, despite the slight difference between them.
10. Adding extra salt to an already salted broth: this habit, common out of taste reflex, needlessly worsens sodium intake already at play.
11. Returning to solid food in a single heavy meal: after several days of near-exclusively liquid, salty intake, an abrupt return places heavy demand on a little-used digestive system and a barely stabilised sodium balance.
12. Underestimating the fibre and vitamin shortfall built up over time: any broth, whatever kind, supplies almost none.
13. Trusting the feeling of fullness as proof of nutritional safety: feeling satisfied by a hot liquid says nothing about actual nutrient intake.
14. Running several broth cleanses close together without reassessment: protein shortfall and cumulative sodium intake do not necessarily resolve between two closely spaced cleanses.
15. Overlooking an ongoing treatment for blood pressure, the heart or the kidneys: these situations are among those that call for the most caution before considering the practice.

Comparing bone broth fasting with other fasting practices

The table below places bone broth fasting among other practices often confused with a strict fast, plus a daily eating window for scale. The difference in nature from a water-only fast stands out clearly: broth keeps an intake, small but real, which classes it among modified fasts rather than strict fasts.

This table confirms what this article has argued since its introduction: the more manageable hunger of bone broth fasting does not, for that reason, place it in a different safety category from other prolonged restrictive practices. Our page on the limitations of BMI makes a related point in a different register: felt comfort never tells the whole story about a real nutritional situation.

Conclusion

Bone broth fasting is, strictly speaking, no longer a fast: as soon as a salted liquid replaces water alone, the practice becomes a modified fast. Salt and warmth make hunger more bearable, but nutritional intake stays very low, and cumulative sodium over several days deserves particular attention, without any figure this page will offer.

If this practice interests you, the first useful step remains assessing, with a health professional, what it genuinely changes given your blood pressure, your treatments and your usual diet – rather than trusting how comforting the broth feels.