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One large meal per day in a 4-hour window. The Warrior Diet approach.
Last updated: February 21, 2026
20 hours
Fasting Window
4 hours
Eating Window
1,200
Est. Weekly Deficit (cal)
~0.34 lbs
Est. Loss per Week
The 20:4 protocol, also called the Warrior Diet, involves fasting for 20 hours and eating within a 4-hour window each day. It was popularized by Ori Hofmekler and is based on the idea that human bodies perform better in a fasted state during the day and can absorb more nutrients in a concentrated evening meal. In practice, most people eat one large meal plus a small snack within the 4-hour window. The calorie restriction from such a tight window is significant.
Choose a 4-hour eating window, typically in the evening (5pm to 9pm is common). During the 20-hour fast, you may consume small amounts of raw vegetables, fruits, or a small serving of protein (under 100 calories) as a light pre-workout fuel without technically breaking the spirit of the protocol, though strict versions prohibit any calories. Eat your main meal at the end of your window. Getting adequate protein in one or two meals requires deliberate planning.
| Day | Eating | Fasting |
|---|---|---|
| Monday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
| Tuesday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
| Wednesday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
| Thursday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
| Friday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
| Saturday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
| Sunday | 5:00pm to 9:00pm | 9:00pm to 5:00pm |
Experienced IF practitioners who have mastered 18:6 and want more aggressive fat loss
People who prefer eating one or two large meals rather than many smaller ones
Anyone who finds eating during the day disruptive to focus and productivity
Beginners and anyone who exercises in the morning and needs immediate post-workout nutrition. The 20-hour fasting window makes morning training nutritionally challenging and increases muscle breakdown risk.
Intermittent fasting controls when you eat. What you eat during the eating window still determines whether you lose fat, maintain muscle, or stall entirely. The most effective approach is scanning your meals with FitCommit as you eat, so you know your daily protein, calorie, and macro totals without logging every ingredient manually. Point your camera at your plate, and the AI identifies the meal and calculates the nutrition in seconds.
Tracking your eating window nutrition takes less than two minutes per day and eliminates the guesswork that causes most IF practitioners to either undereat protein (causing muscle loss) or overeat calories (negating the fast). The combination of a proven fasting schedule and accurate nutrition tracking produces results that neither approach achieves alone.
Track Your Eating Window with FitCommitNot if your protein intake during the eating window is adequate. Eat at least 0.7 to 1.0 grams of protein per pound of bodyweight during your 4-hour eating window. Resistance training three to five days per week provides the muscle-preserving signal. Studies show well-designed intermittent fasting with adequate protein preserves lean mass as effectively as continuous calorie restriction.
The most effective approach depends on your goals. Training in a fasted state (just before your eating window opens) maximizes fat oxidation but may reduce peak performance. Training at the start of your eating window is often the best compromise: you can eat your pre-workout meal immediately before, then refuel with protein within 30 to 60 minutes after. Avoid training more than two hours after your last meal during the fasting window if you tend to feel lightheaded.
Most people see a drop of two to four pounds in the first week, almost all of which is water weight and glycogen depletion. True fat loss begins in week two. At the typical calorie reduction from 20:4 Fast (Warrior Diet) (roughly 1,200 calories per week deficit), expect 0.5 to 1.0 lb of fat loss per week after the initial water weight phase. Visible body composition changes typically appear after four to six weeks of consistent adherence.
20:4 Fast (Warrior Diet) is not suitable for pregnant or breastfeeding women, people with a history of eating disorders, those with Type 1 diabetes or insulin-dependent Type 2 diabetes, or anyone under 18. People on blood pressure or blood sugar medications should consult their doctor before starting any fasting protocol, as medication timing may need to be adjusted. If you experience persistent dizziness, extreme fatigue, or heart palpitations, stop the protocol and speak with a healthcare professional.
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