20:4 Fasting Schedule Warrior Diet Planner

On 20:4 you fast for 20 hours and eat within a 4-hour window each day, for example 4 PM to 8 PM. It's sometimes called the Warrior Diet. With only one or two meals, it's important to eat enough protein, vegetables, fruit and healthy fats in that window. It's an advanced plan: build up from 16:8 or 18:6 first, and don't use it if you're pregnant, breastfeeding, underweight, under 18 or have a history of eating disorders.

Plan one substantial meal and one smaller meal or snack in your 4-hour window. Build each around protein (eggs, fish, chicken, lentils, beans or yoghurt), vegetables and whole grains, with some healthy fat. Eating too little on a short window is easy, so check your calorie target in the BMI & Calories tab and don't aim far below it.

Both are daily time-restricted eating plans. On 16:8 you fast for 16 hours and eat within an 8-hour window, for example noon to 8 PM. On 18:6 you fast for 18 hours and eat within 6 hours, for example 2 PM to 8 PM. 16:8 is the most popular starting point because it mostly uses the hours you are asleep. 18:6 adds two more hours in the fat-burning stage, but it is harder to keep up, so most people build up to it gradually from 14:10 or 16:8.

In the first 0–4 hours your last meal is digested and insulin brings blood sugar back to a steady level. From about 4–12 hours insulin falls and your body uses the sugar stored in your liver (glycogen) while digestion rests. Around 12–16 hours glycogen runs low and your body switches more to burning stored fat. After about 16 hours ketone levels rise (mild ketosis) and research suggests autophagy, the body's recycling of worn-out cell parts, increases. These timings are typical averages: your meals, activity and metabolism shift them.

Intermittent fasting isn't suitable for children and teenagers, during pregnancy or breastfeeding, for people with a history of eating disorders, or for anyone underweight. If you have diabetes, take medicines that lower blood sugar or blood pressure, or have another medical condition, talk to your doctor before you start. Stop and eat if you feel dizzy, faint or unwell.

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