Nutrition & Supplements
Bone Broth
Bone broth breaks a fast. It contains protein, fat, and calories, which trigger digestion and a metabolic response, so by any strict definition it ends the fasted state rather than extending it.
You may also see bone broth called keto-friendly, or a way to stay in ketosis. That claim is closer to true, but it answers a different question. Ketosis is governed mainly by carbohydrate and insulin, not by calories alone, and bone broth is low in carbohydrate, so a cup will not usually push a fat-adapted person out of ketosis. It does not deepen ketosis either, and it still breaks a strict fast, because the protein raises insulin modestly and the calories register. Breaking a fast and staying in ketosis are two separate questions, and bone broth sits on opposite sides of them.
The nuance is in how strict your fast is. On a clean fast, where the goal is to consume nothing with calories, bone broth is off the table. On a dirty fast, where small amounts of food are accepted in exchange for easier adherence, some people drink it deliberately, valuing the electrolytes, the protein, and the feeling of warmth and fullness during a long fast. That is a reasonable tradeoff to make consciously, but it is a tradeoff, not a free pass: the broth still interrupts the strict fasted state.
Mechanistically, the protein in bone broth provides amino acids that can raise insulin and signal mTOR, the growth pathway that fasting lowers, which is part of why calorie-bearing liquids are not fast-safe in the strict sense. If your aim is autophagy or a clean metabolic fast, water, black coffee, plain tea, electrolytes, and certain non-caloric supplements are the items that keep the fast intact.
