What Really Happens to Your Body Inside 36 Hours of Fasting? The Jaw-Dropping Hour-by-Hour Reveal

So, you’ve decided—or at least wondered—what exactly happens to your body if you skip a meal… or two… or an entire day and a half? Fasting for 36 hours might sound like a spiritual journey or a cruel prank your stomach plays on you, but the hour-by-hour transformations happening beneath your skin? Honestly, pretty mind-boggling. Some folks swear it’s like hitting the “reset” button on your body’s operating system, rebooting everything from insulin levels to muscle preservation. Now, I’m not saying everyone should jump on this hangry train without a safety net (please, check with your doc first), but if you’ve ever been curious about what your body’s really up to during those famished hours, this fasting timeline breaks it down like a boss. Ready to see what turning off the snack machine for 36 hours can do? Let’s dive in. LEARN MORE.

The hour-by-hour impact fasting for 36 hours can have on your body is seriously mind-boggling.

Although fasting isn’t for everyone, and nor it should be, it has been claimed that it can give your body a ‘full reset’.

When done safely with adequate hydration, it is claimed to provide various health benefits with each passing hour, according to Doctor Hiltz.

And that’s why a fasting timeline can give you a little bit of an idea on what to expect if you decided to go without food for 36 hours.

It, of course, isn’t recommended for everyone, and you should certainly seek medical advice before going on a fast, but here’s what happens if you do it for just 36 hours.

36-hour fasting timeline

Four hours into the fast

36 hours of fasting can have a big impact on your body (Getty Stock Images)

So, after four hours without eating, your insulin level typically drops and the body starts to burn stored sugar, a simulation video on YouTube channel Wellness Wise states.

This is considered to be the ‘anabolic phase’, a process where your body builds mainly muscle tissue.

Eight hours later

Your blood sugar levels will usually decrease and then your glycogen will be used for energy.

The ‘catabolic phase’, as it’s known, will take the energy from the foods you’ve previously eaten.

12 hours later

After 12 hours, fat will start to burn off as insulin levels decrease again. This process is known as ‘ketosis’.

People who want to lose weight will sometimes go down the fasting route (Getty Stock Images)

16 hours later

16 hours later, a process called autophagy takes place. It’s a cellular process where a cell breaks down and recycles its own components, like damaged proteins or organelles, to maintain energy and cellular health.

Doctor Hiltz reports that exercise and resistance training helps the autophagy process because if it gets disrupted, it can cause ‘problems associated with abnormal cell growth’.

24 hours later

24 hours in is where you start to see major cellular repair, where inflammation reduces and insulin sensitivity improves.

Wellness Wise has provided a simulation of what a 36 hour fast can look like. Watch below:

30 hours later

At the 30 hour mark, this is when the growth hormone spikes, which helps to preserve muscle and promote fat loss.

36 hours later

Finally, maximum autophagy is reached at 36 hours, clearing dead cells, regenerating tissues, and boosting metabolism, providing a full body reset.

The problem with fasting

One issue with fasting is that there aren’t loads of human-backed studies, given that most are done with animals.

“There [are] a lot of proposed benefits to [running on fats]. But a lot of the research hasn’t really [been borne out in] human beings. So we don’t see dramatic health benefits, certainly in the short term,” James Betts, professor of metabolic physiology at the University of Bath, told The Guardian.