The Science Behind Extended Fasting: What Happens to Your Body When You Don’t Eat

The video explores the effects of fasting on the brain, organs, and muscles. It mentions David Blaine’s 44-day fast and Angus Barbieri’s record-breaking year-long fast. Fasting is said to have cognitive and health benefits, such as increased growth hormone levels, decreased hunger hormones, and the production of ketones as an alternative fuel source for the body. Fasting has been found to improve mood, alleviate anxiety and depression, and yield positive health outcomes. However, extended fasting can lead to muscle loss and potential health risks, and it is important to approach fasting with caution and expert guidance.

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Key Insights:

  • Fasting can have significant health and cognitive benefits, including increased growth hormone levels and decreased hunger hormone levels.
  • During fasting, the body shifts from relying on glucose for energy to producing ketones, which serve as an efficient fuel source for the brain.
  • Fasting can lead to improvements in mood, alertness, and emotional well-being.
  • Longer fasts, while potentially beneficial for weight loss and improving certain health conditions, can also result in muscle loss and other negative consequences if not properly managed.
  • Ketones help protect muscle from breakdown and can prevent hunger cravings.
  • The hunger-lowering effect of fasting may be due to reduced insulin levels and improved leptin signaling.
  • Electrolyte supplementation can be beneficial during fasting to prevent fatigue and maintain energy levels.


In 2003, stunt artist David Blaine spent 44 days without food suspended in a transparent box above London. He didn’t even go to the bathroom for a month and a half. But this stunt pales in comparison to Angus Barbieri, a Scottish man who entered the Guinness Book of World Records in 1971 for surviving a year-long fast. So, what happened to Blaine and Angus?

Fasting has gained popularity for its health benefits, both physically and cognitively. Even one or two days of fasting can result in significant improvements. After a day of fasting, there is an increase in growth hormone levels and a decrease in the hunger hormone ghrelin. Brain-derived neurotrophic factor, a protein that promotes brain growth, increases 3.5 fold after 48 hours of fasting. And after a 72-hour fast, the fat storage hormone insulin drops.

Fasting has been practiced for over a hundred years, with reports of miraculous health improvements. However, it is not a new phenomenon. In 1911, Upton Sinclair published a book called „The Fasting Cure,“ detailing the positive effects of multiple day fasts.

During fasting, the body shifts to rely on stored sugar or glucose in the liver for energy. However, when the glucose stores run out, the body starts generating an alternative fuel source called ketones. Ketones become the primary source of energy for the brain during fasting, providing more energy per unit of oxygen used. Ketones have been found to stimulate the growth of brain cells and improve cognitive function.

People who fast for longer periods often report increased focus, energy, and improved mood. Hunger tends to disappear after a few days, and fasting has been associated with improvements in depressive symptoms and emotional well-being.

Longer fasts have also shown significant health improvements. Studies have reported improvements in diabetes, obesity, and other health conditions after extended fasting. However, excessive fasting can have negative consequences, including muscle loss and potential heart problems.

When fasting for extended periods, the body starts breaking down muscle for energy. Proper nutrition, protein intake, and low-intensity exercise can help preserve muscle during fasting. Ketones also protect muscles from breaking down.

It should be noted that excessive fasting without proper monitoring and support can be dangerous. There have been cases of heart problems associated with prolonged fasting, especially beyond 40 consecutive days. However, some individuals have successfully completed longer fasts without ill-effects, such as Angus Barbieri, who fasted for 382 days.

Fasting can have varying effects on hunger. Ghrelin, the hunger hormone, decreases during fasting, making people feel less hungry. Fasting can also lower insulin, which blocks the brain’s ability to register the fullness signal from leptin.

Electrolyte imbalances can make fasting uncomfortable, but this can be managed by supplementing with electrolytes.

In conclusion, fasting can have numerous health benefits, but it should be approached with caution and proper monitoring. While fasting can result in weight loss, it is essential to maintain muscle mass and ensure overall well-being.