This past week, I embarked on a 72-hour fast, consuming only water, black coffee, clove green tea, electrolytes, and L-Glutamine. It was a practice of discipline, metabolic flexibility, and cellular healing—no easy feat, but ultimately an experience that reinforced the amazing adaptability of the human body. This wasn’t about weight loss but rather about reconnecting with our primal design, resetting at a cellular level, and experiencing the benefits of fasting for gut health and immune rejuvenation. Here’s a breakdown of what happened over the course of these three days.
Day 1: The 24-Hour Mark
As I hit 24 hours without food, my body shifted gears. I’d burned through most of my glycogen stores (the quick-access fuel we get from carbohydrates) and entered a state called lipolysis, where fat stores are broken down for energy. This switch to fat as fuel means the body starts producing ketones, a stable, long-lasting energy source that benefits the brain and body alike.
With glycogen depleted, ketones became the brain’s primary fuel, which is why I felt alert and focused, even without food. During this early stage of fasting, I noticed mental clarity setting in, which many people report as one of the perks of fasting. Meanwhile, autophagy—the body’s way of cleaning out cellular waste—was beginning to ramp up. Damaged proteins and cell parts were being broken down and recycled, reducing inflammation and clearing out old cells, which sets the foundation for long-term health and resilience.
At this point, my gut was also getting a break from digestion, allowing the mucosal layer (the gut’s protective barrier) to start rebuilding and healing. I included L-Glutamine as part of my regimen to support this process since it’s known to help fortify the gut lining. I also noticed I wasn’t feeling hunger pangs, which I attribute to metabolic flexibility; years of eating a species-appropriate diet have helped my body easily switch between glucose and fat as energy sources, so hunger simply wasn’t an issue.
Day 2: The 48-Hour Mark
By the second morning, I was 48 hours into the fast. I woke up without any hunger and powered through a kettlebell workout, a quick walk with the dog, and a 3-mile bike ride to work. This was the point where I felt fasting’s effects kick in even deeper. With ketones now in full effect, my brain was running on a steady supply of energy, which kept me sharp and focused. Autophagy was intensifying, giving my cells a thorough “spring cleaning,” breaking down damaged proteins, and discarding anything that no longer served the body.
This cellular recycling isn’t just housecleaning; it’s a process linked to longevity and reduced disease risk. In the gut, autophagy played a key role in healing, especially with the mucosal layer. By now, the human growth hormone (HGH) had also peaked, which helped preserve lean muscle mass even without calorie intake. Some studies show that HGH levels can increase by up to 500% at this point, explaining why I felt confident lifting weights and biking as usual without worrying about muscle loss.
Fat burning had fully kicked into gear as well. With insulin levels at a low point, my body was in a prime state to break down fat for fuel. The absence of food reduced immune triggers in the gut, allowing my mucosal lining to repair itself and strengthening the gut barrier that prevents leaky gut and systemic inflammation.
Day 3: Closing in on 72 Hours
The final morning arrived with one of my first real challenges—a headache. I addressed it with 32 oz of water and a teaspoon of Redmond Real Salt before jumping into an upper body kettlebell workout and another walk with the dog. By now, I could feel the slight fatigue setting in, but it didn’t stop me from hitting my usual activity, including a total of 6 miles on the bike as I neared the end of the 72-hour mark.
Hunger never showed up throughout the fast, which I credit again to metabolic flexibility. Having built up my body’s ability to efficiently switch from glucose to fat stores, I had a constant energy source to tap into, making fasting feel surprisingly manageable. This experience reinforced the power of a species-appropriate diet to enable the body to thrive, whether in a state of feast or famine.
At this stage, autophagy and immune cell renewal were at their peak, clearing out old immune cells and making way for stronger, more efficient ones. HGH remained high, protecting my muscle mass while supporting recovery. Insulin sensitivity was improving, and my metabolism was fine-tuning itself for long-term efficiency. My gut, meanwhile, was well into repair mode, with the mucosal layer continuing to strengthen in the absence of food triggers.
Reflections on the Fast
Reaching the 72-hour mark was not just a physical achievement but a mental one as well. Fasting taught me to trust my body’s innate ability to adapt, repair, and maintain resilience, even without food. By reducing the need for constant feeding, I felt liberated from the demands of modern eating patterns. This experience reminded me that skipping a meal isn’t a crisis—it’s an opportunity for the body to reset and recalibrate. Our ancestors lived with periods of both feast and famine, and this fasting journey reconnected me with that primal wisdom.
Ultimately, this fast was about more than just discipline. It was a chance to step back, let my body do what it’s designed to do, and prove to myself that food doesn’t control me. When you become metabolically flexible, hunger isn’t an emergency, and you gain the freedom to trust in your body’s capabilities.
For anyone curious about fasting or wondering how to develop metabolic flexibility, I encourage you to explore it gradually and consult a professional if you have questions or health concerns. Fasting may not be for everyone, but it’s a powerful reminder that the human body is designed to thrive, adapt, and heal in remarkable ways.
If you’re interested in learning more or want guidance on incorporating these principles into your own health journey, reach out. I’m here to help you discover the amazing resilience of your own body.