What Happened When I Didn't Eat for 72 Hours
The Curiosity, the Questions, and the Why
When I told people I was doing a 72-hour water fast, their reactions ranged from wide-eyed disbelief to intense curiosity. "Why?" was the most common question, followed closely by "But... how?"
Truth is, I was inspired by Dr Mindy Pelz, a fasting expert who talks a lot about the healing benefits of extended fasts, particularly the magic that happens after the 48-hour mark. I wanted to experience that magic for myself: the autophagy, the apoptosis, the mental clarity, the stem cell regeneration. And maybe a little smugness that I did not eat for three whole days.
So, for everyone who's been asking, this blog is for you. I’ll walk you through exactly what happened, what I ate (or didn’t), how I felt, what my blood readings were, and how I structured it—and how you can try it too, safely, mindfully, and with your own health in focus.
How to Prepare for a 72-Hour Fast (Without Losing Your Mind)
Before you dive into a fast, preparation is everything. I didn’t just stop eating cold turkey — I prepared my body by:
Reducing carbohydrates for a few days beforehand
Prioritising sleep
Making sure my electrolytes were ready to go (salt, cream of tartar, magnesium)
Ordering a blood glucose and ketone monitor (essential — more on that below)
Mentally committing: I told myself this was a healing journey, not a punishment
I also chose my timing wisely. I did the fast while staying on our farm, a peaceful and grounding environment, far away from distractions and family meal prep duties. I was over an hour from the nearest shop, which made it much easier to stick to my commitment — no food was in the house to tempt me. I also made sure I had space for rest and short walks each day to support circulation and encourage my lymphatic system to keep moving.
The Science Behind Fasting: Why It Works
Fasting isn't just about skipping meals — it's a powerful metabolic intervention. When you stop eating, your body transitions from using glucose for fuel to burning fat. This process triggers the production of ketones, which fuel your brain and body cleanly and efficiently.
Most importantly, fasting activates two critical processes:
Autophagy: Literally meaning "self-eating," autophagy is the body’s natural process of cleaning out damaged cells, misfolded proteins, and cellular debris. It’s like a spring clean for your cells.
Apoptosis: Programmed cell death. This is how your body identifies and removes malfunctioning or damaged cells that could turn into disease.
Together, autophagy and apoptosis help reduce inflammation, protect against chronic disease, and may even promote longevity.
Research in recent years has shown that extended fasting may:
Improve insulin sensitivity
Reduce systemic inflammation
Support immune function and cellular regeneration
Slow the progression of neurodegenerative diseases
A 2020 review in Cell Metabolism highlighted the role of fasting in reducing inflammation and improving metabolic markers, while a 2022 article in Nature Reviews Endocrinology linked extended fasting protocols to better outcomes in autoimmune and metabolic disorders.
Why You Absolutely Need to Monitor Blood Glucose and Ketones
Throughout the fast, I regularly measured my blood glucose and breath ketone (acetone) levels. This wasn’t just a curiosity — it was a key part of understanding what was happening inside my body and making sure I stayed safe.
Here’s why:
Glucose tells you how low your sugar levels are dropping and how stable your energy is.
Ketones tell you how deep into fat-burning and healing mode (ketosis) you are.
Together, they give you the GKI (Glucose Ketone Index) — a powerful marker of when you’re entering therapeutic ketosis, autophagy, and even apoptosis. A GKI under 1.0 is considered therapeutic — and mine dropped well below that during the fast.
If you’re going to do an extended fast, get a monitor. I used a basic blood glucose/ketone meter and a breath ketone device that measured acetone in ppm (parts per million). The readings helped me understand when to take electrolytes, when to rest more, and when my body was hitting that deep healing phase.
Day 1: Goodbye Glycogen, Hello Growling Stomach
The first 24 hours are generally the most mentally challenging. Hunger came in waves — usually at mealtimes — but I reminded myself that hunger isn’t an emergency. It's just a passing signal.
I sipped water constantly and kept electrolytes topped up. A pinch of salt under the tongue worked wonders for the occasional dizziness, and I had black coffee and matcha to keep me focused and a little comforted.
By the end of Day 1, my blood sugar had dropped and ketones were starting to rise. Nothing dramatic, but the metabolic shift was beginning.
Day 2: The Metabolic Switch Flips
This is where things got real. By the 36-hour mark, my body had used up its glycogen stores and was now burning fat for fuel. My breath ketone readings (acetone) were rising fast, and my blood sugar was consistently low — but stable.
What surprised me most was the sense of calm. I wasn’t jittery. I wasn’t tired. In fact, I was sharper and clearer than I had been in weeks. This is the magic Dr Mindy Pelz talks about — when the brain starts running on ketones, you feel deeply focused and oddly peaceful.
Yes, there were moments of hunger, but they were manageable. Electrolytes were key. I even managed a short walk through the bushland around the farm and felt energised afterward. Movement helps stimulate lymphatic drainage and maintain insulin sensitivity, so even gentle walking is a wonderful support.
Day 3: Deep Ketosis, Autophagy, and (Probably) a Bit of Apoptosis
By hour 48, I was in what’s known as therapeutic ketosis. My GKI (Glucose Ketone Index) dropped below 1.0 — a strong indicator of autophagy (cellular clean-up) and apoptosis (removal of damaged cells).
I continued to take blood glucose and breath ketone readings. My acetone levels peaked at 63 ppm and glucose dropped as low as 2.6 mmol/L — and I felt completely fine. No weakness, no brain fog — just clear, calm energy.
What was most fascinating was how my body had completely switched gears. I was now running on fat and ketones, and it felt effortless.
Breaking the Fast: Gently Does It
At the 72-hour mark, I broke my fast gently with a small, nourishing meal: cooked vegetables, avocado, and some olive oil. A few hours later I had wild salmon and sautéed greens. I avoided sugar, starches, or heavy proteins at first to give my digestive system a chance to wake up.
Despite refeeding, my ketones remained high and my blood sugar barely nudged upward. My GKI stayed below 1.0 for a full day after breaking the fast — which shows how well my body handled the transition.
The Morning After: A New Baseline
The next morning, I took another reading: 4.0 mmol/L glucose, 59 ppm acetone. My GKI was still around 0.73. That’s therapeutic territory — after food. I’d lost about 2.8kg, but I wasn’t interested in the scale. What mattered was how I felt: clear, light, focused, and deeply grounded.
Who Might Benefit from Fasting?
Extended fasting has been studied for its impact on a wide range of conditions. While it’s not a cure-all, research is increasingly showing potential benefits for:
Cancer: Fasting may improve the effectiveness of chemotherapy and help protect healthy cells during treatment. It may also reduce circulating tumour cells (CTCs) — the rogue cancer cells that travel through the bloodstream and contribute to metastasis. Studies suggest that fasting can make cancer cells more vulnerable to treatment while protecting healthy cells, a concept known as differential stress resistance.
Autoimmune conditions: It may reduce inflammatory cytokines and support immune system recalibration.
Insulin resistance and type 2 diabetes: Fasting helps restore insulin sensitivity and reduce circulating glucose.
Neurodegenerative diseases: Ketones provide a clean fuel for the brain and may protect neurons from oxidative stress.
And most notably — inflammation. Chronic inflammation is at the root of nearly every modern disease, and fasting is one of the most powerful anti-inflammatory tools we have. By lowering insulin, activating autophagy, and reducing oxidative stress, fasting allows the body to shift from a reactive state to a regenerative one.
A Few Surprises (and Lessons) Along the Way
Hunger isn’t constant. It comes in waves — and passes.
Salt is not optional. It’s essential to keep your brain and body functioning.
Electrolytes matter more than you think: sodium, potassium (I used cream of tartar), and magnesium were all part of my daily intake.
Monitoring your body with tools like glucose and ketone meters helps you stay informed and motivated.
Gentle walking really helps — physically and mentally.
My body is smarter than I thought. It knew exactly what to do without food.
Coming out of the fast is just as important as going in — refeeding mindfully is key.
Would I Do It Again? Absolutely — But With Intention
This fast wasn’t about deprivation. It was about creating space for healing, clarity, and resetting. It gave me a deeper appreciation for my body’s ability to shift gears and do the work it’s designed to do — if I just step back and let it.
For anyone curious about trying it, I’d recommend starting with shorter fasts (like 16:8 or 24 hours) and building from there. Learn how your body responds. Get comfortable with electrolytes. Listen to your hunger — and your intuition.
And if you're inspired, check out Dr Mindy Pelz — she’s an excellent resource for fasting protocols, especially for women.
Final Thought
Sometimes the most powerful thing you can give your body... is a break.
And I’ll be honest — not having to think about food for three days? That was kind of amazing too.