Can You Eat Soup During Intermittent Fasting?

Can you eat soup during intermittent fasting without breaking your fast? The answer depends on the type of soup and the fasting protocol you are following. Plain broths with minimal calories sit at one end of the spectrum, while cream-based or pulse-heavy soups clearly end the fasted state. Understanding how different soups affect insulin levels, calorie balance and fasting physiology can help you make informed choices that align with your health goals. This article covers which soups are compatible with fasting, what UK guidelines say, and when to seek professional advice.

Does eating soup break an intermittent fast?

Any soup containing meaningful calories will break an intermittent fast by triggering an insulin response. Whether this matters depends on your fasting protocol and personal goals.

Whether soup breaks an intermittent fast depends on its calorie content and the fasting protocol you are following. Most recognised approaches to intermittent fasting, including the 16:8 method and the 5:2 diet, define the fasting window as a period of minimal or zero calorie intake.^[2][3] Any soup that contains meaningful amounts of protein, fat, carbohydrate or calories will therefore end the fasted state and begin your eating window.

The reasoning behind this is physiological. When you consume calories, your body responds with hormonal changes, including a rise in insulin, which signals a shift away from the metabolic processes that fasting is intended to support.^[8][13] These effects are well described in the scientific literature, though the degree to which a very small calorie intake disrupts fasting physiology in any individual will vary depending on the composition of the food and personal metabolism.

It is also worth noting that autophagy, the body's cellular clean-up process that some fasting protocols aim to promote, is a theoretical benefit of fasting that has been demonstrated mainly in animal studies; the evidence in humans remains limited and the calorie threshold at which it is interrupted is not precisely established.^[4]

The practical impact depends on your goals. If you are fasting primarily for metabolic health, weight management or blood glucose control, consuming a calorie-containing soup during your fasting window would technically break the fast. If your goal is more flexible, for example reducing overall daily calorie intake rather than achieving strict metabolic fasting, a low-calorie soup may fit within your personal approach without significantly undermining your results.

It is important to be clear about your fasting method before deciding. Strict protocols such as water fasting allow only water, black coffee or plain tea. More flexible approaches, such as the 5:2 diet, may accommodate very low-calorie foods or broths during restricted days. Understanding which category your chosen method falls into is the essential first step. The NHS and the British Dietetic Association (BDA) both note that fasting approaches vary considerably in their rules and that individual goals should guide the method chosen.^[2][3]

Which types of soup are safe to have while fasting?

Plain bone broth or clear vegetable broth with low calorie content is most compatible with flexible fasting. Cream-based, pulse, noodle and thickened soups are incompatible with any fasting window.

Plain bone broth or clear vegetable broth with a low calorie content is the type of soup most compatible with flexible intermittent fasting protocols. These liquids provide electrolytes, sodium and some trace minerals without delivering a large calorie load, which means they are less likely to disrupt the hormonal state associated with fasting. It is important to note, however, that broths are not calorie-free and their composition varies widely depending on preparation and brand; they are not appropriate during strict water fasts, which permit only water, black coffee or plain tea.^[7]

For those following a more flexible fasting approach, very low-calorie soups are sometimes incorporated without significantly affecting outcomes. However, there is no universally agreed calorie threshold at which a fast is considered broken; this depends on the protocol and your individual goals. Checking the nutrition information panel for total energy per serving is the most reliable guide, and it is worth comparing both the per-100 ml and per-serving figures, as serving sizes vary considerably between products.

Soups that are clearly incompatible with any fasting window include:

• Cream-based soups such as cream of tomato or leek and potato, which are high in fat and calories

• Lentil, bean or pulse soups, which are rich in protein and carbohydrate

• Noodle or rice soups, which contain significant starchy carbohydrate

• Commercially prepared packet soups, which often contain added sugars, maltodextrin or thickeners that raise the calorie count

Homemade broths, where you control the ingredients, offer the most transparency about calorie and sodium content. If you have hypertension, heart disease or kidney disease, or are following a sodium-restricted diet, be aware that many commercial soups and bouillon products are high in sodium and may not be suitable; the NHS 'Salt: the facts' guidance provides further information on recommended daily limits.^[16]

How does soup affect your fasting window and results?

Calorie-containing soup interrupts reduced insulin secretion and fat oxidation that fasting supports. Carbohydrate-rich soups cause the most pronounced insulin response and are most disruptive.

Consuming calorie-containing soup during your fasting window interrupts the metabolic processes that intermittent fasting is designed to support, including reduced insulin secretion and increased fat oxidation. The degree of interruption depends on the calorie and macronutrient content of the soup and your individual metabolism.

Carbohydrate-rich soups tend to produce a more pronounced insulin response than broths or protein-based soups, and are therefore more disruptive to fasting physiology.^[8][9] The effects of small amounts of protein or fat on fasting-related hormonal changes are less clear-cut, and the evidence in humans is still developing; claims about specific macronutrients and appetite hormones should be understood as general principles rather than established rules for every individual.

For those using intermittent fasting as a weight management strategy, overall calorie balance across the day remains important. Consuming a calorie-containing soup during the fasting window reduces the calorie deficit that fasting is intended to create. Over time, these additions can meaningfully affect results, though consistency over weeks and months tends to matter more than perfect adherence on any single day.

For individuals who find strict fasting difficult to sustain, incorporating a small, low-calorie broth during the fasting window may improve adherence without completely undermining the approach. The BDA notes that the best dietary pattern is one that is sustainable for the individual.

Important safety note: people with diabetes who use insulin or sulfonylureas (such as gliclazide or glipizide) face a risk of hypoglycaemia (low blood sugar) during fasting periods.^[10][11] If you have diabetes and are considering intermittent fasting, you should seek advice from your GP or diabetes care team before starting. Diabetes UK provides specific guidance on fasting and diabetes management.^[17] If you are unsure how to balance these considerations, speaking with a registered dietitian or your GP is advisable.

Can I drink broth or bouillon during a fast?

Plain broth or bouillon is widely used in flexible fasting protocols and provides electrolytes with minimal calories, typically 15 to 40 kcal per 240 ml. It is not appropriate during strict water fasts.

Plain bone broth and bouillon are among the most commonly used liquids during flexible intermittent fasting protocols, and for many people they are considered acceptable within the fasting window of approaches such as the 5:2 diet or extended eating-window methods. Bone broth typically provides a small amount of protein (from collagen and gelatin), electrolytes and sodium, with a calorie content that varies considerably depending on preparation and brand; figures from UK nutrition databases suggest typical ranges of around 15 to 40 kilocalories per 240 ml serving for homemade or lightly prepared broths, though commercial products may differ.^[6] Bouillon cubes dissolved in hot water tend to be lower in calories, primarily providing sodium and flavour.

The appeal of broth during fasting is practical: it can help manage hunger, replenish sodium lost through reduced food intake, and provide a warm drink that feels more substantial than plain water. It is worth noting that even small amounts of protein, such as those found in bone broth, may have some effect on insulin levels and could theoretically affect autophagy in strict fasting protocols; however, the human evidence on this is limited and the clinical significance for most people following flexible fasting is uncertain.^[4][9]

For those focused on weight management or blood glucose control, the calorie contribution of plain broth is unlikely to be significant. For those pursuing strict water fasting, broths are not appropriate as they contain calories.

When choosing a commercial bouillon or broth product, check the label for:

• Added sugars or maltodextrin, which raise the carbohydrate content

• Artificial flavourings or thickeners, which may add hidden calories

• Sodium content, which can be very high in some products

If you have hypertension, heart disease, kidney disease or are on a sodium-restricted diet, high-sodium broths and bouillon may not be suitable for you. The NHS 'Salt: the facts' guidance sets out recommended daily sodium limits. Homemade bone broth or a simple bouillon cube in hot water remains the most straightforward option for those who want to control both calorie and sodium content.

What do NHS and nutrition guidelines say about fasting and food?

The NHS supports intermittent fasting as one weight management option but recommends GP advice for anyone with underlying health conditions. The BDA advises fasting is unsuitable for pregnant women, under-18s, and those with diabetes or eating disorders.

The NHS acknowledges intermittent fasting as one approach to weight management, noting on its Live Well pages that methods such as the 5:2 diet can be effective for some people when followed safely.^[1][2] NHS guidance emphasises that any eating pattern should still provide adequate nutrition across the week and should not lead to nutrient deficiencies. The NHS does not endorse any single fasting protocol as superior, and it recommends that people with underlying health conditions speak with their GP before starting any fasting regimen.

NICE guidance on obesity management supports a range of dietary approaches, including calorie restriction and structured eating patterns, as part of a broader weight management plan.^[14][15] NICE recommends that dietary interventions are tailored to the individual and delivered with appropriate support, rather than followed in isolation. There is no specific NICE guidance on intermittent fasting and soup consumption, but the general principle that calorie intake should be accounted for across the day applies.

The BDA's Food Fact Sheet on intermittent fasting notes that fasting approaches are not suitable for everyone. The following groups should not fast for weight loss without first seeking medical advice:

• Pregnant or breastfeeding women

• Children and young people under 18

• People who are underweight or have a history of eating disorders

• Older or frail adults

• People with diabetes, particularly those using insulin or sulfonylureas, due to the risk of hypoglycaemia

• People with kidney disease, heart disease or other complex health conditions

From a nutritional standpoint, registered dietitians in the UK generally advise that the quality of food consumed during eating windows matters as much as the timing of meals. Soups can be a nutritious and practical meal option during eating windows, particularly those based on vegetables, legumes or lean protein.

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, for those exploring structured approaches to weight management.

If you are considering intermittent fasting and are unsure whether it is appropriate for your health circumstances, your GP or a registered dietitian is the right first point of contact. For urgent concerns about symptoms arising during fasting, contact NHS 111 for advice.

Scientific References

1. Overweight and obesity in adults.
2. How to lose weight | Weight loss tips and advice.
3. The influence of time-restricted eating on weight management and metabolic health.
4. The effect of fasting or calorie restriction on autophagy induction.
5. Food labels.
6. Composition of Foods Integrated Dataset (CoFID).
7. The effect of black coffee on fasting metabolic markers and the implications for intermittent fasting.
8. Quantifying Dietary Glycemic Load and Insulin Demand for Chronic Disease Prevention and Management.
9. A protein-rich meal provides beneficial glycemic and hormonal responses as compared to meals enriched in carbohydrate, fat or fiber.
10. Gliclazide: medicine for type 2 diabetes.
11. Is Time-Restricted Eating Safe in the Treatment of Type 2 Diabetes? A Review of Intervention Studies.
12. Impact of Ramadan Diurnal Intermittent Fasting on Hypoglycemic Events in Patients With Type 2 Diabetes.
13. Intermittent fasting and 'metabolic switch': Effects on metabolic syndrome, prediabetes and type 2 diabetes.
14. Overweight and obesity management (NG246).
15. Overweight and obesity management | Physical activity and diet chapter (NG246).
16. Salt in your diet.
17. Diabetes - Type 2.

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