Intermittent fasting (IF) restricts the daily eating window. Most commonly 16:8 (16-hour fast, 8-hour eating window) or 14:10.
Mechanism: The fasting window allows insulin to drop, autophagy to upregulate, and circadian metabolism to align. The benefits come mostly from the resulting caloric reduction and improved meal-time consistency, less from any mystical fasting state.
Use case: Skip breakfast or skip dinner. Both work. 14:10 captures most of the benefit with much less behavioral cost than 18:6 or 20:4.
Caveats: IF doesn't outperform straight caloric restriction in head-to-head trials. Women with HPA fragility, athletes in heavy training blocks, and underweight individuals should be cautious.