Fasting involves intentionally restricting calories to encourage specific metabolic shifts, such as depleting stored glucose reserves and transitioning to burning fat for fuel (ketosis). A common confusion for those fasting is whether consuming any liquid other than plain water will halt this metabolic state. The question of whether savory liquids, such as broth, can be consumed without breaking the fast is frequent, as these liquids contain small amounts of calories and nutrients.
Broth and the Caloric Threshold
The primary metabolic goal of fasting is to keep the hormone insulin at a low level, which signals the body to stop storing energy and begin accessing fat reserves. Consuming anything that causes a significant insulin spike will interrupt this process, effectively ending the fast. Broth is often considered permissible because it typically contains minimal calories and very few carbohydrates, which are the main triggers for insulin release.
Most experts agree on a general “caloric ceiling” for liquids consumed during fasting to maintain metabolic benefits. This commonly accepted guideline is to keep intake below 50 calories per serving. A standard cup of bone or vegetable broth usually contains less than 50 calories, placing it within this threshold for most fasting protocols focused on metabolic health.
While a strict, water-only fast is required for processes like autophagy, low-calorie broth is generally accepted for “dirty fasting.” For the purposes of maintaining ketosis and fat-burning, the minimal calorie and carbohydrate content of broth is generally considered negligible. The type of calories consumed also matters, as fat and protein found in broth have a less dramatic impact on insulin compared to simple carbohydrates.
Ingredient Guidelines for Fasting Broths
Whether a broth is suitable for fasting heavily depends on its ingredients, making label scrutiny or careful preparation essential. Commercial broths, while convenient, frequently contain hidden ingredients that can inadvertently break a fast. Check the nutrition label for added sugars, such as dextrose or maltodextrin, which trigger an insulin response.
The carbohydrate and sugar counts must be zero or near-zero per serving to be considered fasting-friendly. Beyond sugars, store-bought broths may contain yeast extracts, natural flavors, or starches designed to thicken the liquid, contributing to the caloric load. These additives can stimulate digestion and potentially compromise the fasted state.
For homemade broths, it is best to use minimal amounts of high-carbohydrate vegetables, such as carrots, and to discard all solid vegetable matter before consumption. Simmering animal bones with herbs, spices, and small amounts of non-starchy vegetables like celery and onion, then straining the liquid thoroughly, yields a clean broth. This preparation ensures that only the liquid, with its minimal calories and nutrients, is consumed, avoiding the fibrous carbohydrates that would require digestion.
Electrolyte Balance and Managing Hunger
One of the most practical benefits of consuming broth during a fast is its ability to support electrolyte balance, which is often disturbed during periods of caloric restriction. Fasting causes the kidneys to excrete more sodium and water, which can lead to a depletion of minerals like sodium, potassium, and magnesium. This mineral imbalance frequently results in discomfort, including headaches, fatigue, and dizziness, commonly referred to as “fasting fatigue.”
Consuming a savory broth, particularly one seasoned appropriately with salt, helps replenish these lost electrolytes, supporting nerve signaling and muscle function. This simple replenishment can significantly improve comfort and adherence to a fasting schedule. The minerals extracted from bones and vegetables during the simmering process provide a gentle way to maintain hydration without compromising the low-insulin state.
Broth offers a psychological advantage that aids in managing hunger. The warm, savory flavor provides the satisfying sensation of consuming food without the caloric load that would end the fast. The minimal protein content found in bone broth can also contribute to satiety, helping to suppress appetite and curb cravings.