The human body is a fascinating thing. The effects that eating or not eating can have on you are immense.

In a simulation set to show what 36 hours of fasting can do to a body, people find out what happens over time when they don’t eat. And it is a lot more intense than you thought.

Keep reading to learn more.

While some people may fast for religious reasons, there are others who tend to do it for health reasons. While some people may be skeptical, a lot of those who observe fasting claim that it does wonders for their physical and mental health.

According to experts, at Medical News Today, it can help to regulate blood sugar as well as improve insulin sensitivity when it is performed in a safe manner.

Now a new YouTube video is showing what happens inside your body when you fast for 36 hours. The video shows what happens at ever four hour intervals inside a person’s body when they are abstaining from food and drink.

After four hours of fasting, the body stops digesting food. This is known as a ‘catabolic phase.’ An expert, Dr. Kiltz 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’.

After eight hours of fasting, your blood sugar begins to drop and your body starts to use stored glycogen for energy as it can no longer depend on new food coming in to replenish your energy.

Then 12 hours in, your body is depleted of glucose, which causes your liver to begin breaking down fat into fatty acids called ketones. The process of turning ketones into food is known as ‘metabolic switching,’ which is what triggers weight loss.

After 16 hours of fasting, autophagy, a cellular process, begins. According to the Cleveland Clinic, this makes the cell disassemble its junk parts and repurpose what is salvageable and turn them into new parts.

And then 24 hours into fasting, is when major cellular repair begins to take place in the body. Your body is now in full fat-burning mode, reducing inflammation and improving your insulin sensitivity.

Then, 30 hours into it, the growth hormone spikes. This helps preserve muscle and helps with fat loss. According to the YouTube video, this is where the process of ‘deep healing’ begins.

Then, at the 36-hour mark, you reach the stage for maximum autophagy, and your body begins to regenerate tissues and boost your metabolism.

The reset can go as far as 72 hours.

However, researchers remain divided on how beneficial fasting is for the body because of lack of data.

“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, a professor of metabolic physiology, said in an interview.

A study according to News In Health also showed that people who regularly fast for 16 or more hours a day are at a higher risk for gallstones. Other side effects include of course, intense hunger and food cravings. Some issues with digestion, irritability and low moods among other things.

The benefits of fasting can vary from person to person so it is always advisable to consult a medical professional before embarking on fasting.