Misty forest path in the Dutch countryside

Reset your body.
Reclaim your health.

Guided prolonged fasting retreats in the Dutch countryside — designed for people who’ve tried everything else.

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Prolonged Fasting

What if the body already knows how to heal?

You already know the advice. Eat better. Move more. Sleep longer. And yet something still feels off. Once your metabolism falls out of balance, the right habits stop being enough. Most health struggles come from a metabolism that is been pushed beyond its limits: it needs a complete reset.

Participant resting during a guided fasting retreat

The Problem

Insulin resistance silently drives weight gain, fatigue, and brain fog — and it is far more common than most people realise. Mitochondrial dysfunction robs your cells of the energy they need to function, leaving you exhausted in ways sleep cannot fix. Chronic low-grade inflammation keeps your body in a constant state of emergency. Standard diets and exercise treat symptoms; they rarely reach these root causes.

The Reset

Prolonged fasting triggers mechanisms no other intervention can match. Insulin levels drop to their baseline, reversing resistance at the cellular level. As glycogen depletes, ketosis shifts your fuel source from volatile glucose to clean, stable energy derived from fat. And autophagy — activated only during extended fasting — clears damaged cellular machinery, reducing inflammation at its root.

Energy

Consistent, stable energy replaces the peaks and crashes. Better sleep follows naturally as cortisol normalises and cellular repair kicks in.

Clarity

As ketones replace glucose as brain fuel, the fog clears. Sharp, sustained focus without stimulants.

Metabolism

Insulin sensitivity improves, fat-burning becomes effortless, and chronic inflammation drops measurably.

Hunger

Counterintuitively, prolonged fasting resets your relationship with hunger. Most participants end up eating less, and enjoying food more.

My Story

I was patient number six.
Then I became the researcher.

Not long ago, I hid in a storage room at work just to lie down. Brain fog so severe it felt like someone had injected horse tranquilizer into my brain. I couldn't focus, couldn't remember simple things, couldn't function. I was in my late twenties supposedly in my prime — and I felt worse than the average retiree. I tried everything. Sleep tests, blood work, five different GPs , every diet under the sun. At my last doctor's visit, I broke down. All she could offer was a referral to a psychologist. I wasn't depressed. I was tired of being tired.

Out of desperation, I signed up for a 7-day water fasting retreat in the Hungarian countryside. People thought I was crazy.

By day five, a wave of clarity I hadn't felt in years. The exact opposite of brain fog. One of the best feelings of my life.

When I returned to Amsterdam, the results were undeniable. 7kg gone, mostly fat. Sleep transformed. Brain fog: gone. It felt like someone had pressed the factory reset button on my entire body.

Osiris Retreats exists because that reset shouldn't be a secret. And it shouldn't require flying to Hungary to find it.

Credentials

  • BSc Molecular Biology
  • BSc Human Movement Science
  • MSc Chemistry
  • Background in pharmaceutical research & data analytics
Rutger Schim van der Loeff, founder of Osiris Retreats
Cozy nature cabin in the Dutch countryside
The Retreat

Three days.
A real reset.

A guided fast in the Dutch countryside, held in a small group of 6–10 participants. Every detail — from your preparation to your refeeding meal — is designed to make your fast both safe and transformative.

Dates

September 2026

Location

The Netherlands

Group size

6–10 participants

Duration

3 days

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