It depends on the blend. Ground mushroom coffee brewed with water has under 5 calories and does not break a fast. Instant mixes such as Ryze add MCT oil and coconut milk powder, about 15 to 20 calories per tablespoon, which matters little for weight loss and ends a strict fast.
| Calories | ~5-20 kcal per serving |
|---|---|
| Breaks a weight-loss fast? | No |
| Breaks ketosis? | No |
| Breaks autophagy? | Partial |
| Insulin impact | Minimal |
Most mushroom coffees combine regular or half-caf coffee with extracts of lion's mane, chaga, reishi or cordyceps. The mushroom extracts add almost no calories. What changes the count is the creamy base some brands use: powdered coconut milk and MCT oil add a little fat, which barely affects insulin but still counts as energy.
Claims about focus, immunity or stress come mostly from cell and animal studies, and human evidence is thin. Mushroom coffee usually has less caffeine than regular coffee (Ryze lists about 48 mg per serving), which some people find easier on an empty stomach. Adding milk, oat milk, honey or sugar breaks the fast exactly as it does with regular coffee.
One or two cups during the fasting window are fine for weight loss and ketosis. For an autophagy or water fast, use a plain ground mushroom coffee or black coffee with nothing added.
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