Intermittent Fasting Time Range

Intermittent Fasting: Protocols, Autophagy & Practical Guide

Intermittent fasting (IF) means you switch between an eating window and a fasting one. You'll run into a handful of common protocols: 16:8 (16h fasting, 8h eating, the one Martin Berkhan made popular with his Leangains method), 18:6, 20:4 (Ori Hofmekler's Warrior Diet), and 24h OMAD (One Meal A Day). What this calculator does is suggest a fasting window based on your age and how experienced you are, because if you're new to it you really should start around 12–14h and build up from there.

Here's what's happening inside. Roughly 3 hours after your last meal, blood insulin falls, which lets the body start pulling from fatty acids (lipolysis). Around the 16h mark, autophagy picks up speed. That's the cellular housekeeping process Yoshinori Ohsumi described, work that earned him the Nobel Prize in Physiology in 2016. Growth hormone (GH) climbs, and ketone bodies (β-hydroxybutyrate) step in as a backup fuel for neurons.

Applications

People turn to IF for body recomposition, metabolic flexibility, better insulin sensitivity, cutting fatty liver (NAFLD), keeping meal planning simple, and it shows up in longevity research too. The Brazilian Society of Exercise and Sports Medicine (SBME) considers it safe for healthy adults as long as calorie and protein intake stay where they should. Athletes commonly run IF alongside strength training so they don't lose lean mass.

FAQ

Can I drink water, coffee or tea during the fast? Yes. Plain water, black coffee and unsweetened tea won't break the fast, and they tend to take the edge off hunger.

Who should avoid intermittent fasting? If you're pregnant or breastfeeding, dealing with anemia or type 1 diabetes, have a history of disordered eating, are a child or teen, or take insulin or sulfonylureas, do NOT fast without a doctor watching over it.

Is this medical advice? No. Treat this calculator as educational, nothing more. Talk to a registered physician or nutritionist (CRN) before you start any fasting protocol, and especially so if you're on medication or living with a chronic condition.