Shocking simulation shows what happens to your body when you fast for 36 hours and the extreme impact

A viral YouTube simulation with over 28 million views details the effect a 36-hour fast can have on the body and gives an insight into one of the most talked-about modern health trends.

Fasting has long been practised for a range of reasons, from religious observance to weight management, and it continues to draw attention online as creators and wellness pages offer increasingly dramatic explanations of what happens when the body goes without food.

That fascination has helped push one clip from Wellness Wise to a viral viewership, with the short video presenting a stage-by-stage look at how the body responds as the hours without eating begin to mount.

Focusing on the internal changes linked to fasting, the simulation reveals how fasting causes shifts in energy use and how the body adapts over time. While fasting is a practice that isn’t ideal for everyone, health experts like those at Medical News Today have agreed that those who do take part safely have the potential to better regulate their blood sugar levels, along with improving insulin sensitivity.

Whichever your opinion, the simulation provides a full breakdown from hour four to the 36-hour mark.

Your body goes through some mind-boggling changes if you don't eat food for 36 hours (YouTube/Wellness Wise)

What happens to your body during a 36-hour fast?

Four hours

In a 55-second video, posted to YouTube by Wellness Wise, it’s revealed that after four hours of fasting, your body 'stops digesting food, insulin drops, and it starts burning stored sugar for energy'.

According to popular practitioner Doctor Kiltz, this is the start of what is known as the ‘catabolic phase’.

On his website, Klitz Health, he says this period is ‘characterized by the breakdown of larger molecules of stored energy into smaller energy molecules which are mobilized to fuel your cells’.

Eight hours

When you haven't eaten for eight hours, this is the time when sugar starts to drop in your blood, and your body begins to use stored glycogen for energy instead of relying on new fuel coming in, as per the YouTube video.

12 hours

After 12 hours, your body is depleted of glucose, causing your liver to start breaking down fat into fatty acids called ketones — AKA, starting ketosis.

This process of turning ketones into food is known as ‘metabolic switching’ and, according to the BBC, is the reason why fasting can lead to weight loss.

Different things happen to your body the longer you abstain from food (Getty Stock Image)

16 hours

When you reach the 16th hour of a fast, a cellular process known as autophagy takes place. As per the Cleveland Clinic, this allows the body to disassemble its damaged cells and toxins — repurposing the salvageable bits and pieces into new, usable cells.

As the Wellness Wise video explains, this is essentially 'recycling'. Dr Hiltz explains that exercise and resistance training also help the autophagy process because if it gets disrupted, it can cause 'problems associated with abnormal cell growth'.

24 hours

A full day without food is a pretty long time for most, but this 24-hour mark is where major cellular repair takes place in the human body.

As also explained in the YouTube video, your body is fully in fat-burning mode, reducing inflammation and improving insulin sensitivity.

30 hours

The growth hormone spikes 30 hours after fasting, which reportedly helps to preserve muscle and promote fat loss.

Wellness Wise also states that this is the period where ‘deep healing’ begins.

36 hours

If you fast for 36 hours, then you’ve reached the stage of maximum autophagy, where your body regenerates tissues and boosts your metabolism after clearing out dead cells.

This full-body reset can be extended to upwards of 72 hours if you want to, as well.

What do researchers say about fasting?

Experts are divided on whether or not fasting is good for the body, with some claiming a lack of human-backed studies renders making conclusions difficult.

James Betts, professor of metabolic physiology at the University of Bath, told The Guardian: “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.”

Meanwhile, studies have also found that people who regularly fast for more than 16 or 18 hours a day have a higher risk of gallstones, as per News In Health.

Other potential fasting side effects include intense hunger and food cravings, various digestive issues, irritability, and low moods. Mark Mattson, a Johns Hopkins neuroscientist, argues that there are myriad benefits that come with fasting.

He says: “Many things happen during intermittent fasting that can protect organs against chronic diseases like type 2 diabetes, heart disease, age-related neurodegenerative disorders, even inflammatory bowel disease and many cancers,” he says.

Remember, everyone reacts differently to fasting; so, it’s worth checking with your medical professional before taking part in the practice.