The three most common time-restricted intermittent fasting protocols differ by how long you fast and how long you eat. 16:8 fasts 16 hours and eats 8. 18:6 fasts 18 hours and eats 6. 20:4 fasts 20 hours and eats 4. Each protocol has different benefits, difficulty levels, and lifestyle fits.
This guide compares the three head-to-head and helps you decide which schedule suits your goals and your life.
Quick comparison
| Protocol | Fasting | Eating | Difficulty | Best for |
|---|---|---|---|---|
| 16:8 | 16 hours | 8 hours | Beginner | Daily sustainable practice |
| 18:6 | 18 hours | 6 hours | Intermediate | Stronger results without OMAD |
| 20:4 | 20 hours | 4 hours | Advanced | Aggressive calorie restriction |
How each protocol works
16:8 divides your day so you fast for 16 hours and eat within an 8-hour window. A typical schedule is to stop eating at 8:00 PM and eat again at noon the next day. Most of the fast happens during sleep, which is why 16:8 is the most beginner-friendly protocol.
18:6 extends the fast by 2 hours. You might stop eating at 7:00 PM and start at 1:00 PM the next day. The longer fast pushes the body deeper into fat-burning states but requires more discipline, especially in the morning hours.
20:4 is sometimes called the Warrior Diet. You fast for 20 hours and eat within a 4-hour window. Most people eat one large meal and one smaller meal in this window, or sometimes a single meal that bridges OMAD territory.
Difficulty progression
Each protocol is meaningfully harder than the one before. The progression from 16:8 to 18:6 to 20:4 is not linear.
16:8 asks you to skip breakfast, essentially. For most people, this is manageable within 1 to 2 weeks of practice.
18:6 asks you to delay your first meal by 2 more hours into the day. By noon you are normally hungry, and pushing through to 1:00 PM takes more effort. After 2 to 4 weeks, most people adjust.
20:4 asks you to wait until mid-afternoon to eat. By this point, the morning hunger has passed but you still need to compress your full day's nutrition into 4 hours. The challenge is less about hunger and more about getting enough calories and nutrients in a short window.
Potential benefits of each
All three protocols share core benefits associated with intermittent fasting: improved insulin sensitivity, easier calorie management, and metabolic flexibility. The differences are in degree.
16:8 benefits:
- Easier to sustain long-term
- Compatible with most social and work schedules
- Allows three solid meals or two meals plus snacks
- Strong fit for couples and families who eat together at lunch and dinner
18:6 benefits:
- Slightly stronger calorie restriction
- Deeper time in fat-burning states
- Two meals per day instead of three
- Often produces faster results than 16:8 for the same effort level
20:4 benefits:
- Significant calorie compression
- Extended autophagy windows
- Time savings from fewer meals
- Often used by people who plateau on 16:8 or 18:6
Lifestyle fit
The right protocol depends as much on your daily life as on your goals.
Choose 16:8 if you:
- Eat lunch with family or coworkers
- Exercise in the morning and need fuel
- Are new to intermittent fasting
- Want a sustainable long-term protocol
- Have a stressful job and want minimal added willpower load
Choose 18:6 if you:
- Are comfortable with 16:8 but want more results
- Can delay lunch by an hour or two
- Want two meals per day instead of three
- Are looking to break through a plateau
Choose 20:4 if you:
- Have practiced 16:8 and 18:6 successfully
- Have time-flexible meal scheduling
- Want stronger calorie restriction without going to OMAD
- Are not training heavily in the morning
Combining protocols
You do not have to pick one protocol forever. Many practitioners cycle between protocols based on the day or week.
A common pattern:
- Weekdays: 16:8 because lunch with coworkers is easier
- Weekends: 18:6 or 20:4 with a relaxed schedule
Another pattern:
- High-activity days: 16:8 to support energy needs
- Rest days: 18:6 or 20:4 because energy demands are lower
This flexibility lets you match the protocol to your real life rather than forcing your life around the protocol.
Common mistakes across all three
Eating too much in the eating window. Compressing meals does not help if you compensate with larger portions of low-quality food.
Drinking calorie-containing beverages during the fast. Coffee with cream, "skinny" lattes, and bone broth all break the fast.
Going too aggressive too fast. Jumping from a normal eating pattern to 20:4 typically leads to giving up. Build gradually.
Skipping protein. Without enough protein in your eating window, you may lose muscle alongside fat regardless of which protocol you pick.
Ignoring electrolytes. Longer fasts deplete sodium, potassium, and magnesium. Add a pinch of salt to your water if you experience headaches or fatigue.
What about 14:10 or 12:12?
Shorter fasting windows like 14:10 (14 hours fast, 10 hours eating) and 12:12 are gentler entry points. They are not always grouped with the standard intermittent fasting protocols, but they are useful stepping stones.
If 16:8 feels too aggressive on day one, start with 12:12 for a few days, then 14:10, then move to 16:8. The body adjusts more reliably with gradual progression.
How to track different protocols
Switching between 16:8, 18:6, and 20:4 manually requires you to track different start and end times each day. A fasting tracker app simplifies this. You pick the protocol for the day, tap start, and the timer adjusts automatically.
Easy Fast supports all three protocols plus OMAD, 5:2, and custom schedules. The app stores your history locally so you can see how different protocols affect you over time.
Frequently asked questions
Which is better, 16:8 or 18:6?
16:8 is better for sustainability and beginners. 18:6 is better for stronger results when you have already practiced 16:8. Neither is objectively better. The right choice depends on your experience level and goals.
Is 20:4 better for weight loss?
20:4 typically produces faster weight loss because the eating window is more restricted, leading to lower calorie intake. However, sustainability matters more than intensity. 16:8 done consistently for a year often produces better results than 20:4 done for 2 weeks before burning out.
Can I switch between fasting protocols?
Yes. Many practitioners cycle protocols based on day, week, or season. Switching is fine as long as you eat enough on each protocol to sustain your activity level.
Does 18:6 cause more autophagy than 16:8?
Research suggests longer fasts produce more autophagy, but the exact thresholds are not fully established. Both protocols likely activate cellular cleanup processes to some degree.
Which protocol does Easy Fast support?
Easy Fast supports 16:8, 18:6, 20:4, OMAD, 5:2, and custom schedules. You can switch between protocols at any time.
Easy Fast is a free intermittent fasting tracker for iPhone that supports all major fasting protocols. Download Easy Fast on the App Store.
Ready to start tracking your fasts?
Easy Fast is free to download. Track 16:8, 18:6, 20:4, OMAD, and 5:2 with one tap.