A new simulation has offered insight into what happens to your body after a day and a half without food.
Fasting, the practice of abstaining from food for a set period, has surged in popularity due to its benefits, which range from weight loss and improved metabolism to disease prevention.
Many adopt it for religious reasons, others for fitness goals, and some for mental clarity. But despite its widespread appeal, health professionals have warned that not eating for extended periods, particularly without medical supervision, can have serious consequences.
A simulation, posted by the YouTube channel The Limitless Emperor, uses graphics and commentary to show the fascinating changes taking place in your body during an extended fast.
Watch below:
Four Hours In
At the four-hour mark, your body has finished digesting the last meal. Insulin levels drop rapidly, signaling your body to start burning stored glucose for energy rather than processing new food.
Eight Hours In
Blood sugar levels continue to fall, and your body begins to tap into its “backup reserves”, which is glycogen – a form of stored glucose.
Twelve Hours In
At twelve hours, significant changes begin to occur, such as your body shifting from burning glucose to burning fat, a process called ketosis.
This is where the body starts to use fat as fuel, producing ketones that help power the brain and body. Many people report reduced appetite and increased fatigue during this stage, as ketone production rises.
Sixteen Hours In
This marks the beginning of autophagy, a cellular process where the body breaks down and recycles damaged cells.
While this can help to repair tissue and flush out waste, experts caution that the benefits of autophagy are not yet fully understood, and more research is needed to determine its role in disease prevention and treatment.
Twenty-Four Hours In
By the twenty-four-hour point, the body is now burning fat more efficiently, with all cells working overtime in what’s called “cellular repair.”
Cellular repair accelerates, and inflammation begins to decrease. Additionally, insulin sensitivity improves, making it easier for your body to regulate blood sugar in the future.
Thirty Hours In
At this stage, growth hormone levels surge, which may help protect muscle mass and promote faster recovery from physical exertion.
Thirty-Six Hours In
After 36 hours, the body hits peak autophagy: “Dead cells are wiped out, tissues regenerate, and metabolism fires on all cylinders.”
Experts Weigh In: Is It Safe?
While the simulation paints an intriguing picture of the benefits of a 36-hour fast, experts remain divided on the long-term effects and potential risks.
Some studies suggest intermittent fasting can have health benefits, like protecting organs against chronic diseases, but many researchers, such as James Betts, Professor of Metabolic Physiology at the University of Bath, warn that “a lot of the research hasn’t really [been borne out in] human beings,” per The Guardian.
Betts warned that fasting for extended periods might not deliver dramatic short-term health benefits, despite the claims made by fasting enthusiasts.
Additionally, long-term fasting has been linked to potential risks, including gallstones and side effects like irritability, digestive issues, and low mood, particularly when fasting beyond 16 to 18 hours.
On the other hand, researchers like Mark Mattson, a neuroscientist at Johns Hopkins, argue that fasting can have protective effects.
“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 shared.
Should You Try a 36-Hour Fast?
Health professionals strongly recommend starting with shorter fasting periods, like the popular 16/8 method, before attempting longer fasts.
It’s also important to stay hydrated during fasting periods, preferably with water or zero-calorie drinks, and to break your fast carefully. Overeating after a fast can lead to discomfort and may negate some of the benefits of the fasting process.
