The practice of fasting has gained significant attention as a potential tool for improving health, but what exactly occurs inside your body when you stop eating for three days? According to health experts, the process involves several distinct phases, moving from immediate fuel switching to deep cellular cleansing, though it’s not without its risks.
During the first 24 to 48 hours, your body exhausts the stored sugar in your liver, known as glycogen. Since glycogen holds onto water, this initial phase often results in a noticeable drop in water weight. As sugar stores deplete, the body pivots to its secondary fuel source: fat. This metabolic shift leads to the production of ketones, which become the primary source of energy, powering everything from muscles to the brain, and can even lead to improved mental clarity for some.
The most significant changes are said to occur around the 72-hour mark. This is when a process called autophagy is believed to significantly accelerate. Often described as the body’s internal recycling program, autophagy cleans out damaged cells and components, including intracellular pathogens like viruses. Additionally, a prolonged fast of this duration may stimulate the regeneration of the immune system by triggering the production of new stem cells.
However, medical professionals universally caution that extended fasting is not for everyone. It can cause side effects like fatigue, dizziness, and constipation. It is strongly discouraged for pregnant women, individuals with diabetes, those with a history of eating disorders, or anyone at risk of bone loss. Consulting a healthcare provider before attempting any prolonged fast is an essential first step to ensure it can be done safely.
