anti-aging The Biological Reset: What Actually Happens to Your Body During a 72-Hour Fast New 2025 research reveals that a 72-hour fast can spike HGH by over 1,200% and trigger immune stem cell regeneration. Learn the biological timeline of prolonged fasting and how to track your metabolic stages with the new Harduex Fasting Planner. By Harduex 22 Dec 2025