Health

I Lost 6.6 Pounds In 72 Hours And Felt My Senses Come Alive—The Science Behind It Will Shock You

Published on October 30, 2025

I never thought I’d voluntarily go three full days without food. Like most people, I believed that skipping meals was dangerous — something that would leave me dizzy, weak, and miserable. But curiosity got the best of me after watching a doctor explain what happens to the human body during a 72-hour fast.

So, I decided to try it — carefully, with lots of research, water, electrolytes, and rest. Over those three days, I ended up losing 3 kilograms (about 6.6 pounds), but what surprised me most wasn’t the weight loss. It was how my senses changed, how my mood stabilized, and how I rediscovered my relationship with food.

Before I go any further, I want to make something clear: this is my personal experience, not medical advice. Fasting for 72 hours can be intense, and it’s absolutely essential to consult a doctor or nutritionist before trying it yourself — especially if you have diabetes, heart issues, an eating disorder, or any chronic condition.

Why I Tried Fasting — and What Science Says Happens When You Do

Obesity rates in the U.S. are now hovering around 40 percent of adults, and obesity-related cancer deaths have tripled in two decades. It’s no secret that our diets — heavy on processed foods, sugary drinks, and refined fats — have taken a toll.

Doctors like Dr. Eric Berg and researchers from UCLA Health have pointed out that one of the biggest culprits behind weight gain and chronic disease is insulin resistance — when the body stops responding properly to insulin because we eat too often and too much sugar.

The logic behind fasting is simple but profound: if you stop eating for a certain period, your insulin levels drop, giving your body time to switch gears and start burning fat instead of storing it.

But what actually happens when you go three full days without food?

Scientific studies show that after 72 hours, the body goes through several measurable metabolic changes:

Blood sugar and insulin levels fall, which helps the body reset its sensitivity to insulin.
Ketones — chemicals produced when the liver breaks down fat for energy — rise dramatically.
Autophagy, the body’s natural cell-cleaning process, activates. Old or damaged cells are broken down and recycled for energy and repair.
The immune system becomes more efficient, as fasting can stimulate the production of new white blood cells.

Essentially, fasting gives the body a break from constant digestion and lets it focus on repair instead.

The First 24 Hours — Hunger, Doubt, and the Weight of Habit

The first day was the hardest. Around hour 12, my stomach began to protest. By hour 18, every commercial for pizza felt personal. Hunger wasn’t just physical — it was psychological.

I realized how often I eat out of boredom, habit, or emotion rather than genuine hunger. I drank water, green tea, and unsweetened electrolytes to stay hydrated, but I couldn’t stop thinking about food.

Yet something shifted as the hours passed. Around hour 20, my energy dipped, but my mind felt unusually clear. I wasn’t sluggish — just still. The next morning, my body felt lighter, as if I’d released more than just calories.

Day Two — When My Body Found a New Fuel Source

Around 36 hours in, something remarkable happened: my hunger faded.

Instead of craving sugar or bread, I felt calm. My body had begun producing ketones, an alternative energy source made from fat. These ketones fed my brain, and it showed — my focus sharpened, my mood stabilized, and I experienced what many call “fasting clarity.”

Interestingly, research confirms this. After roughly two days, most of the body’s stored glucose (called glycogen) is gone, and ketones become the main energy source. This process not only spares muscle tissue but also reduces inflammation and oxidative stress in the brain.

That evening, as I went for a walk, I noticed how vivid everything smelled. The scent of rain on the pavement, coffee brewing in a nearby café, even the faint salt of the sea air — they all hit me at once. It was as if my senses had been dialed up to full volume.

The Third Day — Autophagy and a Mental Reset

By the third day, my body felt different — lighter, more efficient. I wasn’t sluggish or dizzy. In fact, I felt sharper than usual. My mood was calm, my thoughts clear, and strangely, I didn’t miss food.

Scientists say that after 48 to 72 hours of fasting, autophagy peaks. This process is like a biological recycling program: the body begins breaking down damaged cells and rebuilding new ones. It’s been linked to improved immune function and longevity.

In one study published by the National Institutes of Health, researchers found that prolonged fasting can trigger stem-cell regeneration in the immune system. Another paper in the journal Autophagy showed that this process helps clean up intracellular pathogens — even viruses that normally hide inside cells.

By hour 72, I began re-introducing food gently — starting with bone broth, then fruit, and later a small, balanced meal. I’d lost about 4 kilograms, but more importantly, I’d gained insight into how my body works.

What the Numbers Don’t Show — How My Senses and Mind Changed

The physical changes were visible on the scale, but the mental ones were what stayed with me. My sense of smell and taste sharpened. The first bite of an apple after 72 hours felt electric — juicy, crisp, and alive in a way I hadn’t experienced before.

I became more aware of how food made me feel rather than how it tasted. Meals slowed down. I started eating mindfully — noticing texture, aroma, temperature. Food stopped being background noise and became an experience again.

And something else happened: my fear of hunger disappeared.

Before, I saw hunger as an emergency — something to fix immediately. After fasting, I learned that hunger comes in waves, and that it’s okay to feel it. It doesn’t control me anymore.

That was the most surprising conclusion of all. Fasting didn’t teach me to avoid food. It taught me to respect it.

What the Science Says About 72-Hour Fasting

Here are a few key takeaways backed by credible research:

Ketones as brain fuel: A 72-hour fast increases blood ketone concentration from near zero to over 4,000 µmol/L, providing a steady energy source for the brain.
Improved insulin sensitivity: Studies show intermittent and prolonged fasting can reduce insulin resistance, helping stabilize blood sugar levels.
Immune system regeneration: Research indicates that a 72-hour fast triggers stem-cell activity that helps rebuild white blood cells, potentially rejuvenating immune defenses.

These findings support what I personally felt — more mental clarity, improved digestion, and a sense of internal “reset.”

The Necessary Caution — Why You Shouldn’t Try This Without Guidance

While fasting has scientifically proven benefits, it’s not for everyone. Medical experts emphasize that long fasts should be done under supervision or after consulting a healthcare professional.

Fasting can cause dizziness, electrolyte imbalance, fatigue, headaches, or nutrient deficiencies if done improperly. People with diabetes, heart disease, eating disorders, or pregnant and breastfeeding women should avoid it.

Doctors at the Mayo Clinic and Harvard Health also note that while short fasts can help regulate metabolism, prolonged ones should be undertaken cautiously, especially for those on medication.

If you’re interested in fasting, start small — try intermittent fasting first (like 16 hours of fasting followed by an 8-hour eating window), drink plenty of water, include electrolytes, and break your fast gently.

What I Learned From Three Days Without Food

After my fast ended, I didn’t rush to eat everything I’d missed. Instead, I took my time.

I learned that food isn’t just fuel — it’s connection, comfort, and communication. But when you strip it away for a while, you understand how powerful that connection is.

I no longer eat automatically. I eat intentionally. I listen to my body instead of my cravings.

And that’s the real lesson of fasting — not deprivation, but awareness.

Sources used:

Effects of a 72-Hour Fasting on Brain Metabolism in Healthy Women — National Library of Medicine (NIH)
Effect of Intermittent Fasting Diet on Glucose and Lipid Metabolism in Patients with Metabolic Syndrome — National Library of Medicine (NIH)
The 72-Hour Fast and Its Benefits — Sage Bariatric Institute

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