Fasting, the voluntary abstinence from food, has surged in popularity for its metabolic benefits, including improved health markers and weight management. A common question is whether bone broth, a traditional food often touted for its benefits, compromises the body’s fasted state. This issue balances strict metabolic goals against the practical necessity of sustaining a fast.
Understanding the Fasted Metabolic State
The goal of fasting is to trigger a metabolic switch that moves the body away from using glucose as its primary fuel source. This transition occurs when carbohydrate stores are depleted, causing the body to shift to burning stored fat for energy, a state known as ketosis. A fast is typically considered “broken” when a food or drink stimulates a significant insulin response, shifting it back into a fed state. Keeping insulin levels low is the main objective, as high insulin levels inhibit fat burning.
Prolonged fasting also aims to promote autophagy, a cellular clean-up process where the body removes damaged cells and recycles their components. Autophagy is highly sensitive to nutrient intake, particularly to the presence of amino acids and glucose, which can rapidly suppress the process.
The Nutritional Profile of Bone Broth
Bone broth is created by simmering animal bones and connective tissue for many hours, which extracts various compounds into the liquid. A typical cup contains a low caloric count, often ranging from 30 to 80 calories, and minimal carbohydrates. This low-carb profile means it does not significantly impact blood sugar.
Its most prominent macronutrient is protein, specifically amino acids like glycine, proline, and glutamine, derived from the collagen and gelatin in the bones. A single cup can contain between 6 and 10 grams of protein. While this protein content is relatively small, the presence of these amino acids is the point of metabolic contention, as protein intake can stimulate a measurable, though small, insulin response and potentially inhibit autophagy. Bone broth is also rich in electrolytes and minerals, such as sodium, potassium, and magnesium, which are often depleted during prolonged periods of fasting.
Dr. Fung’s Guidance on Bone Broth Consumption
Dr. Jason Fung, a proponent of therapeutic fasting, views the consumption of bone broth through a lens of practicality and safety, especially for longer fasts. His guidance recognizes the technical metabolic argument while prioritizing the sustainability of the fasting regimen. He recommends bone broth during fasting periods, often alongside water, tea, and coffee.
The primary reason for his recommendation is the maintenance of electrolyte balance, which is often compromised during fasts lasting longer than 24 hours. The sodium, potassium, and minerals in bone broth are crucial for preventing common fasting side effects like headaches, dizziness, and muscle cramps. Fung suggests that the trade-off of a minimal caloric and protein load is acceptable when it helps sustain a longer, more therapeutically beneficial fast.
He emphasizes that the small amount of protein in bone broth does not cause a significant enough insulin spike to completely halt the metabolic shift to fat burning, which is the main goal for weight management and insulin resistance. However, for those whose primary goal is the maximum induction of autophagy, the protein content technically represents a nutrient signal that may interrupt the process. Dr. Fung recommends homemade versions to control ingredients and avoid artificial additives.
Strategic Use During Prolonged Fasting
The decision to use bone broth during a fast should align directly with the individual’s specific health goals and the duration of the fast. For short intermittent fasts, such as the 16:8 protocol, consuming bone broth is generally unnecessary and may be avoided by purists aiming for a strict zero-calorie window. For extended fasts lasting 24 hours or more, bone broth becomes a highly useful tool.
Its strategic use focuses on hydration and nutrient replenishment, particularly for fasts designed to address insulin resistance or weight loss, where the metabolic shift is the main target. To minimize the protein impact on autophagy, it is advisable to limit consumption to small amounts, perhaps one to two cups per day.
Prioritizing a clean, homemade broth is also a practical strategy, as commercial versions often contain higher amounts of protein or added ingredients that could be more disruptive to the fasted state. Use bone broth only when symptoms of electrolyte imbalance first appear.