Fasting for 100 hours (a little over four days) can have profound effects on your body, including fat loss, autophagy, reduced inflammation, and metabolic improvements. Here's a breakdown of what happens during a 100-hour fast, how to prepare, what you can consume, and the best way to break it.
What Happens During a 100-Hour Fast?
Hours 0-12 – Glycogen Depletion & Insulin Drop
- Your body runs on stored carbohydrates (glycogen).
- Insulin levels drop, signalling the body to start tapping into fat stores.
" The journey begins not with emptiness, but with space. In letting go, you make room for what is yet to come. "
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Hours 12-24 – Fat Burning & Ketosis Begins
- Glycogen stores run out, and your body starts using fat for fuel.
- You may enter mild ketosis, where your liver produces ketones for energy.
- Hunger pangs may peak due to the hormone ghrelin but usually pass.
" Observe the hunger, but do not become the hunger. It is simply a visitor, passing through the house of your being. Smile at it, and let it go. "
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Hours 24-48 – Deep Ketosis & Autophagy Boost
- Ketones become the primary energy source.
- Autophagy, your body's cellular cleanup process, increases, clearing out damaged cells.
- Inflammation starts decreasing, and growth hormone levels rise.
- Mental clarity often improves, but you may feel weak or cold.
" You are not tired. You are simply shedding an old way of being. The body resists transformation, but the soul knows the way. "
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Hours 48-72 – Immune System Regeneration & Fat Adaptation
- Stem cell production ramps up, improving immune function.
- Fat-burning is at its peak, with metabolic flexibility increasing.
- Your gut lining begins repairing, reducing inflammation.
- You might feel euphoric due to increased ketones.
" When the body is silent, the mind becomes clear. And when the mind is clear, you can hear the whispers of eternity. "
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Hours 72-100 – Peak Benefits & Hormonal Recalibration
- Insulin sensitivity improves dramatically.
- Human growth hormone is elevated, aiding muscle preservation.
- Your body continues to repair at a cellular level.
- By the end, you might feel highly energised or ready to eat.
" You are not merely fasting from food. You are fasting from distraction, illusion, and attachment. In emptiness, you meet your true self. "
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How to Prepare for a 100-Hour Fast
✅ Ease into it: Try shorter fasts first (e.g., 16-24 hours).
✅ Eat nutrient-dense foods: Prioritize protein, healthy fats, and fibre before fasting.
✅ Hydrate well: Drink plenty of water leading up to the fast.
✅ Electrolyte load: Increase salt, potassium, and magnesium intake before starting.
✅ Cut carbs gradually: This reduces withdrawal symptoms.

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What Can You Consume Without Breaking the Fast?
✅ Water (Cold, Warm, or Hot) – Essential for hydration.
✅ Black Coffee – Enhances fat burning and suppresses appetite.
✅ Green or Herbal Tea – Supports digestion and mental clarity.
✅ Electrolytes (No Sugar) – Salt, potassium, and magnesium prevent cramps.
✅ Apple Cider Vinegar (Diluted) – Helps with insulin sensitivity.
✅ Bone Broth (Minimal Calories) – If absolutely necessary, for minerals.
🚫 AVOID: Artificial sweeteners, milk, or anything with significant calories.
How to Break the Fast Properly
🔹 Start Light – Bone broth, fermented foods (kimchi, sauerkraut), or diluted apple cider vinegar.
🔹 Introduce Healthy Fats – Avocado, olive oil, eggs, or nuts.
🔹 Prioritise Protein – Light meats or fish before heavier meals.
🔹 Avoid Sugar & Junk – Your gut is sensitive; avoid high-carb spikes.
First Meal Example:
- Bone broth with a boiled egg and avocado.
- Followed by a small portion of lean protein and greens.
- Wait 2-3 hours before having a full meal.
Final Thoughts
Fasting for 100 hours is a powerful metabolic reset, but it’s crucial to prepare well, hydrate, and break the fast correctly. If done right, you’ll experience enhanced energy, reduced inflammation, and improved insulin sensitivity.