Extreme 36-Hour Fast Simulation Exposes Shocking Body Changes

Fasting is one of those wellness habits that tends to divide opinions. While some critics question its safety or effectiveness, many who practice it claim it has drastically improved their energy and focus and even helped with weight management.

Others can’t imagine skipping lunch or going a whole day without food. However, with a growing number of influencers, YouTubers, and health sites promoting long fasts to “reset” your body, curiosity about what happens during an extended fast is on the rise.

A recent YouTube video by Wellness Wise has gone viral for laying out precisely what the body goes through during a 36-hour fast, and the changes are quite striking. But while the video gets people talking, not all health experts are on board with the hype.

Before jumping into the timeline of what happens hour by hour, it’s worth remembering that people fast for different reasons: some for religious purposes, some for weight loss, and others for supposed health benefits like better blood sugar control or clearer thinking.

And yes, when done carefully, fasting can lead to specific metabolic changes. However, it’s not a one-size-fits-all approach; for some, it can do more harm than good. Considering that expert opinions on this vary, let’s look at what’s said to happen during a 36-hour fast.

Skipping food for 36 hours sets off a series of unexpected shifts in your body.

4 Hours In: Digestion Takes a Back Seat - Your body has finished digesting your last meal. According to Dr. Kiltz, this kicks off the catabolic phase, where your body starts breaking down stored energy into smaller molecules to keep you going. You’re still feeling okay, and your energy probably hasn’t dipped much.

8 Hours: Sugar Reserves Get Tapped - Around the eight-hour mark, your blood sugar begins to drop. Without new calories, your body shifts to burning stored glycogen for fuel. This is your body’s way of stretching out what’s already available before it needs to go into deeper reserves.

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12 Hours: Fat Becomes the Main Fuel - Once glycogen stores are depleted (usually around 12 hours), your liver breaks down fat into ketones. This process is called metabolic switching, one reason fasting is often tied to weight loss. You’re no longer running on sugar; you’re running on fat.

16 Hours: The Cellular Clean-Up Crew Arrives - After 16 hours, autophagy begins. This is when your cells start clearing out damaged components and recycling useful ones to build new, healthier parts. It’s a kind of internal spring cleaning, and some research suggests it could support long-term health.

According to Dr. Kiltz, exercise during fasting might boost this effect. However, if autophagy is disrupted, it could contribute to abnormal cell growth. That’s one reason fasting isn’t recommended for everyone without proper guidance.

Physiological Insights on Fasting

Dr. Jason Fung, a prominent nephrologist and author of 'The Obesity Code,' emphasizes that short-term fasting can stimulate significant physiological changes in the body, including improved insulin sensitivity and fat oxidation.

His research indicates that even a fast of 16 to 24 hours can lead to increased autophagy, a process where the body cleans out damaged cells, potentially promoting longevity.

Fung's findings suggest that while extreme fasting may trigger rapid body changes, it's essential to approach fasting with caution and gradual integration into one's routine to minimize risks.

For those interested in trying fasting, he recommends starting with intermittent fasting to gauge how your body reacts before attempting longer fasts.

"What Happens When YOU FAST For 36 Hours Straight?"

24 Hours: Deeper Repair Kicks In - Going a whole day without food isn’t easy, but this is the point where your body starts to focus more heavily on repair. Fat burning is fully engaged, inflammation tends to drop, and insulin sensitivity improves temporarily, according to the Wellness Wise video, which has racked up millions of views.

30 Hours: Growth Hormone Rises - Around this point, your body produces more growth hormone. This helps preserve muscle mass and encourages fat breakdown. This stage is also described as when “deep healing” starts, although the scientific backing for that term is less clear.

36 Hours: Maximum Cellular Reset - If you’ve made it this far, you’ve entered the so-called peak of autophagy. Supporters of extended fasting claim this is where full-body regeneration occurs, your metabolism resets, and damaged cells are thoroughly flushed out. While it sounds impressive, there’s still a lot of debate about how much of this applies to humans in the short term.

Is Fasting Good or Bad?

The answer depends on whom you ask. James Betts, a professor of metabolic physiology at the University of Bath, told The Guardian that many of the supposed benefits of fasting haven’t been proven in human studies. “We don’t see dramatic health benefits, certainly in the short term,” he said.

Some research has also linked frequent fasting (over 16 hours a day) with a higher risk of gallstones. Other common side effects include irritability, digestive issues, and increased cravings.

However, not all scientists are skeptical. Neuroscientist Mark Mattson from Johns Hopkins argues that intermittent fasting can lower the risk of several chronic conditions, ranging from heart disease to Alzheimer’s and even some cancers.

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Fasting is complicated. For some, it might offer benefits. For others, it can cause more problems than it solves. If you’re considering trying a 36-hour or extended fasting period, it’s wise to talk to your doctor first. What works for someone else might not work for you.

Your body and its rules should always come first, but your health should always be a priority.

Dr. Mark Hyman, a leading functional medicine expert, highlights the importance of understanding individual metabolic responses to fasting. He notes that while many people report enhanced focus and energy during fasting, others may experience fatigue and irritability.

Hyman suggests maintaining proper hydration and electrolyte balance, which can significantly enhance the fasting experience. He advocates for incorporating nutrient-dense foods during eating windows to support overall health.

Furthermore, he emphasizes that fasting should be tailored to personal health goals and current medical conditions to ensure safety and effectiveness.

Listening to your body's signals is vital; if fasting feels uncomfortable, it may be worth exploring alternative dietary adjustments.

Psychological Insights & Implications

Fasting can undeniably trigger a myriad of body changes, some beneficial and others potentially harmful. Understanding individual responses to fasting is crucial for maximizing its benefits while minimizing risks. Experts like Dr. Jason Fung and Dr. Mark Hyman recommend starting gradually and paying close attention to how your body reacts.

As highlighted by both, maintaining hydration and a balanced diet during eating periods can optimize the fasting experience. Ultimately, consulting healthcare professionals before embarking on any fasting regimen will ensure that your approach is safe and aligned with your personal health needs.