What Shocking Changes Occur Inside Your Body After Just 72 Hours Without Food?

So, you’re thinking about giving up food for 72 whole hours? Yeah, sounds like a punishment reserved for villains in sci-fi flicks—or maybe just the latest fitness craze hyped by influencers with abs for days. We’re bombarded with all kinds of fasting trends these days, from the 12/12 window where you cram all your meals into half a day, to the 5:2 where you pretend you’re starving twice a week. But what if you pushed past those baby steps and went full gladiator mode—no snacks, no meals, nada—for three full days? Crazy, right? Yet, some fitness fanatics swear by it, claiming it sparks this wild body reboot, turning us into walking science experiments. So, what actually happens inside when you starve yourself for that long? Spoiler: It’s not just your stomach growling louder. Ready for a wild ride through hungry hours, cellular clean-ups, and a body on survival mode? Let’s dig in before you decide to starve your soul… and your fridge. LEARN MORE.

Thinking about ditching food for 72 hours? Well, this is what you’re in for.

Dietary fads such as prolonged and intermittent fasting have become increasingly popular online in the past couple of years, as fitness influencers argue that taking a break from enjoying our favourite snacks has various health benefits for our bodies.

You may have heard about trends such as 12/12 fast (which is where you get all your eating done in a 12 hour window) or the 5:2 diet, but what if you were to take things to the extreme and go 24, 36 or even 72 hours without eating any food?

Sounds pretty extreme I know, but it’s apparently something several fitness fanatics have completed over the years.

But what would happen if you turned your body into a live science experiment and did just that?

Eating a clock is optional during fasting (Getty Stock Images)

According to one simulation shared on YouTube, your body triggers a number of mechanisms developed to keep us running without any food.

6-10 hours of fasting

After six to 10 hours without food, the body will have burned through existing stores of nutrients from your last meal.

From this point onwards, your pancreas begins releasing glucagon to regulate your blood sugar levels. You’ll also begin to feel hungry.

16-24 hours of fasting

Make it to 16 hours without eating and a process called autophagy kicks in, which is where your body begins to break down and recycle damaged cells for energy. The video goes as far as claiming this process can kill cancer cells – however, it is important to note is debated by medical experts. Meanwhile, the body will also experience a spike in growth hormones in order to slow down muscle wastage.

Make it past 24 hours without fuelling your body and you will begin to run completely off your fat stores, while the rest of the body goes into deep repair mode.

48-72 hours of fasting

After 48 hours without food the process of autophagy will increase as the body looks for more things to keep it going. Some people may even experience an increase in mental clarity and cognitive benefits, although i’d imagine the hunger would also be pretty intense at this point.

This continues into the third day as the body goes into survival mode, with one study undertaken by researchers at Queen Mary University of London suggesting the body will go through a ‘multi-organ transformation’ at this point.

Perhaps the strangest part of these fasting videos is the fact that your skin seems to vanish without food (YouTube/TrainAiFit)

How safe is it to fast for 72 hours?

It goes without saying that just because some people can exist off nothing but water and black coffee for three days, it doesn’t mean that everyone can.

If it’s weight management you’re looking for, then John Hopkins medicine notes that fasting for too long can cause the opposite effect, as the body enters starvation mode and begins to store fat.

Your body can also experience some pretty grim side effects once it enters into ketosis, with symptoms such as fatigue, headaches and brain fog being reported (via Heathline).

Perhaps it’s worth a chat with your doctor before considering this one.