Can skipping food for 72 hours reset your immune system? Studies say yes

Scientists at USC discovered that a 72-hour fast can trigger stem cell regeneration — effectively rebooting the immune system. It’s not starvation, it’s a biological cleanse that forces your body to rebuild itself from within.

Through a process called autophagy, your cells begin “eating” damaged proteins and faulty mitochondria — turning waste into energy. It’s like spring-cleaning your body at the molecular level.

By the end of the first fasting day, ghrelin — your hunger hormone — starts to calm down. What felt like deprivation transforms into focus, as your brain switches from glucose to pure ketone fuel.

Around hour 36, something strange happens — clarity hits. Ketones flood the brain, lifting fog and amplifying focus. Growth hormone spikes 300%, preserving muscle while burning fat like jet fuel.

As the 48-hour mark passes, chronic pain can fade. Studies suggest fasting reduces inflammatory cytokines — the molecules behind fatigue, joint stiffness, and premature aging. Your body finally exhales.

USC biogerontologist Valter Longo’s research shows prolonged fasting may help weaken cancer cell metabolism — giving healthy cells a head start in regeneration. Simplicity meets survival science.

During fasting, hydration isn’t just about water. Electrolytes like sodium and magnesium act as the body’s lifeline — keeping your heart steady, your muscles firing, and your energy stable through the fast.

The first 72-hour fast feels brutal. The second, manageable. By the third, your body adapts — running cleaner, calmer, sharper. Like software updates, each fast installs a better version of you.

End it wrong and you undo the magic. Start with bone broth, ease in with eggs or avocado, and skip carbs for 24 hours. The refeed is where healing locks in — the difference between rebound and renewal.