Simulation shows what happens to body if you eat no food for three days

A simulation has revealed what happens to the human body if you don't eat food for three days.

A YouTuber shared a breakdown of what happens to your body if you eat nothing for three days. Credit: Peter Dazeley / Getty

As the global obsession with weight loss grows, more people are turning to fasting as a method for losing pounds and improving health.

While skipping meals for a day or two might sound extreme to some, others swear by the benefits. But what happens inside the body when you go without food for an extended period?

A new simulation by the YouTube channel Gravity Transformation takes viewers hour by hour through a 72-hour fast, showing what the body experiences from the moment you skip your first meal to the point where nutrient deficiencies start to become a risk.

The First 6–10 Hours: Burning What’s Left

Within the first few hours of fasting, the body uses up remaining carbohydrates from previous meals.

At this stage, the pancreas releases glucagon to activate "the release of stored glucose from the liver and muscles".

As a result, hunger hormones like ghrelin spike, making you feel hungrier, but this is where many choose to push through.

10–16 Hours: Growth Hormones and Fat Burning

By the 10-hour mark, the pituitary gland begins boosting production of human growth hormone, which helps delay muscle breakdown.

Around hour 16, the body shifts to being more "reliant on burning fat for energy". This is also when autophagy kicks in, which is a process where the body recycles damaged cells, bacteria, and junk proteins.

24–32 Hours: Glycogen Depletion and Fat Reliance

After about one full day, the body runs out of glycogen and becomes "entirely reliant" on fat stores for energy. Protein breakdown slows, allowing muscle to be preserved.

48–72 Hours: Tranquility and Risk

Two days in, the simulation claims that many people experience "improvements in mood, alertness, and tranquility".

But by day three, nutrient deficiencies may start to develop. At this point, experts warn, it's crucial not to continue without medical supervision.

While the simulation provides a look at the body’s response to short-term fasting, real-world cases show that human survival without food can stretch far beyond expectations - particularly in extreme conditions.

In 2012, Swedish man Peter Skyllberg made headlines after surviving an estimated 60 days trapped in a snow-covered car by reportedly eating nothing but handfuls of snow.

Other remarkable examples include illusionist David Blaine, who endured 44 days suspended in a glass box without food, Mahatma Gandhi, who went 21 days consuming only water during a hunger strike, and a Japanese hiker who survived 24 days without food or water after becoming stranded in the mountains.

In 2003, David Blaine spent 44 days suspended in a glass box by the River Thames in London without food. Credit: Michael Loccisano / Getty

According to Professor Stephen Joseph of the University of Nottingham, conditions like isolation, low temperatures, or reduced activity can further increase survival time, as can psychological resilience.

"People can go into flight or fight mode, and will have adrenaline coursing through them. Those adrenaline surges are important because they will determine how people survive," he shared.

But not everyone responds to life-threatening scenarios in the same way, as Joseph noted: "In disastrous situations, survival depends on personalities. Some might catastrophize and lose hope, while others are more hopeful and more resourceful.

"Hope is probably a big key to this," he added.

Featured image credit: Olha Danylenko / Getty