What Is Intermittent Fasting?

Intermittent fasting (IF) is not a diet — it's an eating pattern. Instead of telling you what to eat, it focuses on when you eat. The core idea is simple: cycle between periods of eating and voluntary fasting on a regular schedule.

Humans have fasted for most of evolutionary history. Hunter-gatherers didn't have refrigerators or 24-hour convenience stores. Our bodies evolved to function without food for extended periods, and many religious traditions — from Ramadan to Lent to Yom Kippur — have preserved the practice for millennia [1].

Common Protocols

16:8 (Lean Gains) — Fast for 16 hours, eat within an 8-hour window. The most popular starting point. For most people this means skipping breakfast and eating between noon and 8 PM.

18:6 — A slightly tighter window that many people graduate to after adapting to 16:8. The extra two hours of fasting can deepen ketone production and autophagy.

OMAD (One Meal a Day) — A 23:1 protocol. You eat one large meal per day. This is more advanced and not for beginners, but some people thrive on its simplicity.

5:2 — Eat normally five days a week and restrict calories to roughly 500–600 on two non-consecutive days. Popularised by Dr. Michael Mosley, this approach gives more flexibility on eating days [2].

Extended Fasting (24–72+ hours) — Longer fasts done periodically, sometimes under medical supervision. These push deeper into autophagy and cellular repair but carry more risk and aren't appropriate for everyone.