Fascinating simulation shows what a 24 hour fast does to the body

A new video reveals exactly what happens to your body during a 24 hour fast—and it’s fascinating. 

The 45 second animated clip, created by YouTube account GrowFit Health, visualises in granular detail how abstaining from food for a day can trigger ‘deep repair’.

The video, which has been watched nearly 150,000 times, begins by explaining how in the first four hours the body stops digesting food, insulin levels drop, and the body starts burning stored sugar for energy.

Insulin is a hormone which helps stabilise blood sugar levels. 

Stable blood sugar is linked to a myriad of health benefits including improving mood, more restful sleep, and improved focus.

After eight hours, the video explains, because blood sugar is running low, your body grabs glucagon, which is stored glucose—the chemical term for sugar—to use for energy.

At the 12 hour mark, fasting drives your body to enter a ‘mini’ ketosis mode, which is when your body begins to burn fat, and insulin levels decrease.

After 16 hours, autophagy, the process of your body essentially self-eating old and damaged cells, begins.

And finally, after 24 hours, ‘you’re officially in deep repair mode’, fat is the main source of fuel, inflammation drops, and insulin sensitivity improves.

‘Your body is basically saying, “thanks for the break”,’ the voiceover explained.

In the comment section, there were hundreds of comments from social media users, with many sharing their experience with fasting.

One user commented: ‘I have been doing fast one day per week for like 10 months now. Before that I used to get sick once like every two months, since the last 10 months I have only gotten sick once.’

And a second user commented: ‘It’s a great feeling like this after completing a 72 hours fast.’ 

However, experts have previously urged caution over its ‘short-lived’ effectiveness, warning it can trigger digestive problems and even life-threatening heart disease.

This is because when your body enters the ketosis stage, 12 hours into a fast, the liver begins to break down stored fat into fatty acids called ketones.

High levels of ketones can lead to a condition called ketoacidosis, when blood becomes too acidic—which if not treated promptly, can be life threatening.

Studies have also found that prolonged exposure to ketones can be detrimental, increasing the risk of heart attacks and strokes.

Meanwhile, research has long warned that excessive or prolonged autophagy, which occurs after 16 hours, can lead to cell death, potentially harming organs.

But supporters of an extreme version of intermittent fasting, the OMAD diet, which stands for one meal a day, hail the benefits.

They say it boosts productivity, improves memory and cognition, and helps them manage their weight.

Other intermittent diets, such as the 16:8 eating plan, are based on entirely the same principle.

But followers instead fast for 16 hours a day and eat whatever they want in the remaining eight hours—typically between 10am and 6pm.

This can be more tolerable in than the infamous 5:2 diet, where calories are restricted to just 500 a day twice a week. 

Intermittent fasting has been endorsed by everyone from Hollywood A-listers like Jennifer Anniston to former Prime Minister Rishi Sunak.

Earlier this summer, a major review found intermittent fasting may be no better than regular dieting. 

The team of international researchers found the benefits from fasting were essentially ‘trivial’ compared to normal dieting.

Neither eating meals in a specific time window—like an eight-hour period—or doing fasting for five days of the week and then eating normally for two were any better.