Three daily intermittent fasting schedules come up most often: 16:8 (16 hours fasting, 8 hours eating), 18:6 (18 hours fasting, 6 hours eating), and OMAD (one meal a day, roughly 23 hours fasting). They are often presented as a ladder where a longer fast means more benefit, but the evidence does not support that simple picture. Most of the benefit seen in studies comes from eating less overall and eating more consistently, and the schedule you can keep up matters more than the one that looks most aggressive.
This page compares the three side by side: how hard each is, how each fits protein needs and training, what the research does and does not show, and how to choose or switch between them.
Table of Contents
Quick Comparison
A quick overview of each schedule:
16:8
- Eating window: 8 hours (e.g., 12 PM – 8 PM)
- Difficulty: Usually manageable after 1–2 weeks of adjustment
- Research base: The most studied of the three time-restricted eating schedules
- Sustainability: Generally good
- Protein-target friendly: Yes; two or three meals fit easily
- Social impact: Minimal
18:6
- Eating window: 6 hours (e.g., 1 PM – 7 PM)
- Difficulty: Moderate; adjustment often takes a few weeks
- Research base: Smaller than for 16:8; results are broadly similar
- Sustainability: Moderate to good for people whose schedule fits the window
- Protein-target friendly: Tighter; needs some planning
- Social impact: Can clash with early lunches or late dinners
OMAD
- Eating window: About 1 hour (one meal per day)
- Difficulty: Hard at first; some people find it simpler once adjusted, many do not
- Research base: Limited; few controlled studies
- Sustainability: Highly individual
- Protein-target friendly: Difficult; a full day of protein in one sitting is a lot of food
- Social impact: Significant; one fixed meal per day
16:8 in Depth
What it does well
- Creates a daily fasting window that mostly covers sleep plus a skipped or delayed breakfast
- Has the largest body of research among daily time-restricted schedules, with studies looking at weight, blood sugar, and blood pressure (mostly short-term, with mixed results)
- Fits social life well — a 12–8 PM window covers lunch and dinner
- Two full meals plus a snack suits most adult routines
- Usually the quickest of the three to get used to
Limitations
- On its own it may reduce calorie intake only slightly; results depend heavily on what and how much you eat in the window
- Some trials comparing 16:8 with ordinary calorie reduction found similar weight loss, so the timing itself may add little for some people
- The daily routine can feel monotonous for some
Best for
Beginners, people looking for a schedule they can keep long term, people with busy family or social eating routines, and anyone whose main goal is general health habits rather than rapid weight loss. People taking medication that must be taken with food should check timing with their healthcare provider. See the 16:8 method guide.
18:6 in Depth
What it does well
- A shorter window tends to reduce total food intake a little more than 16:8 for many people
- Still allows two proper meals if they are timed well
- Less disruptive to daily life than OMAD
- A natural next step for people comfortable with 16:8
Limitations
- Hitting protein targets in 6 hours takes planning
- Lunch often moves to 1–2 PM and dinner to 6–7 PM, which can clash with work and family meals
- Adjustment is harder than for 16:8; hunger in the first few weeks is common
- Claims that 18 hours triggers a meaningful jump in autophagy are not established in humans; there is no reliable way to measure it in everyday life
Best for
People who are comfortable on 16:8 and want a slightly shorter window, people whose schedule naturally fits a 1–7 PM eating window, and people who have stalled on 16:8 and want to try a change. See the 18:6 guide.
OMAD in Depth
What it does well
- Simplicity — one decision per day about food
- For many people it reduces total calorie intake, which is the main driver of weight loss
- Saves time on meal preparation
- Some people who have adjusted to it say they like the routine and feel steady energy, though this varies a lot
Limitations
- Getting a full day’s protein in one meal is hard — many people can’t comfortably eat that much protein in one sitting
- Risk of losing muscle is highest of the three if protein and strength training are not deliberate
- A small study comparing one meal a day with three meals at the same calories reported higher fasting glucose and blood pressure with the single meal, so “more fasting” is not automatically better
- The social cost is real — a fixed meal time, often dinner only, limits flexibility
- The strict “fasting vs. eating” structure can encourage binge-restrict patterns in some people; it is not appropriate for anyone with a history of disordered eating
- Generally less suitable for older adults, people who are pregnant or breastfeeding, athletes with high training loads, and anyone on glucose-lowering medication without medical guidance
Best for
Healthy adults who genuinely prefer one large meal, people whose schedule works better with a single meal, and people who have built up gradually from 16:8 and 18:6 and plan protein carefully. See the OMAD guide.
For Weight Loss
All three can support weight loss, and the main reason is the same: a shorter eating window tends to reduce how much you eat. There are no reliable “typical” rates of loss for each schedule — results vary widely with food choices, starting weight, activity, and adherence. Research comparing time-restricted eating with ordinary calorie reduction has generally found similar results when calorie intake is similar.
In practice, a shorter window may lead to faster early loss for some people, but it is also harder to maintain. A pace you can keep for years is more useful than a faster one you drop after a few weeks.
For Muscle Preservation / Building
- 16:8: The most practical option if you are training for strength or muscle. Two or three meals make protein targets easy to reach.
- 18:6: Workable for keeping muscle; harder for building it. Needs deliberate protein at each meal.
- OMAD: The most challenging for muscle goals. Spreading protein over several meals is generally recommended for muscle building, which OMAD does not allow. Better suited to maintaining muscle during a short fat-loss phase than to building it.
Whatever the schedule, regular resistance training and enough total protein matter most. See fasting and muscle.
For Metabolic Health
For markers like insulin sensitivity, blood sugar, blood pressure, and cholesterol, the evidence is still limited and mixed:
- Studies of 16:8 and similar windows have reported modest improvements in some people, often linked to weight loss
- There is little good evidence that 18:6 or OMAD produce larger improvements than 16:8 when weight loss is similar
- Some research suggests eating earlier in the day may matter as much as the length of the fast
If you have type 2 diabetes, fatty liver disease, or another health condition, fasting is not a substitute for medical care. Talk to your healthcare provider before changing your eating pattern, especially if you take insulin or other glucose-lowering medication. See fasting and diabetes and fasting and medications.
For Sustainability
There is little reliable data on how many people stay with each schedule over the long term, and dropout in fasting studies varies widely. In general, the more restrictive the schedule, the harder it is for most people to keep up. Many people who try 18:6 or OMAD end up using 16:8 or a similar window as their everyday default and use longer fasts only occasionally.
Signs a schedule is sustainable for you: you are not constantly hungry or irritable, your sleep and energy are stable, you can eat with family and friends without stress, and you are not overeating when the window opens.
When to Switch Between Them
- Start with 16:8 (or 12:12 or 14:10 first). Usually the right entry point. Give it several weeks before considering anything more restrictive.
- Consider 18:6 if: 16:8 feels easy, you want to try a shorter window, and you have time to plan two protein-rich meals.
- Try OMAD occasionally if: you are comfortable with 18:6, you have a specific practical reason (simplicity, schedule), and you are willing to plan protein deliberately.
- Go back to a longer window if: you are struggling to keep it up, sleep is getting worse, social life is suffering, training performance is dropping, or you notice binge eating.
- Mix them: Some people do 16:8 most days and a shorter window on some days, based on their schedule rather than a strict rule.
Not sure where to start? Try the protocol selector.
Frequently Asked Questions
Is OMAD better than 16:8 because the fast is longer?
Not necessarily. There is no good evidence that the effects grow in step with fasting length. When calorie intake and weight loss are similar, differences between schedules appear small, and OMAD is harder to sustain.
Can I do 16:8 on weekdays and OMAD on weekends?
Some people find a mixed approach convenient. It is a matter of preference and schedule; there is no evidence that varying the pattern is better or worse. Many people actually find the reverse (a longer window at weekends) easier socially.
What about 14:10?
A reasonable beginner step or long-term option. It is less restrictive than 16:8 and fits most routines. Worth considering if 16:8 feels too restrictive.
Is 20:4 (Warrior Diet) different from OMAD?
Slightly. A 4-hour window allows two smaller meals or one larger meal with a snack, which makes protein targets easier than strict OMAD. See our Warrior Diet guide.
I gave up on OMAD. Did I fail?
No. OMAD doesn’t suit most people as a daily long-term pattern. Going back to 16:8 is simply choosing a schedule that fits you.
Which is best for someone over 50?
A gentler window such as 12:12, 14:10, or 16:8, with enough protein and regular strength training, is usually more appropriate. Very restrictive schedules make it harder to eat enough protein, which matters more as muscle mass naturally declines with age. Check with your healthcare provider if you take regular medication. See our fasting after 50 guide.
The Bottom Line
16:8 is a sensible starting point and long-term option for most healthy adults. 18:6 is a reasonable next step if your schedule fits it. OMAD is the hardest to sustain and makes it hardest to eat enough protein, and there is little evidence it offers extra benefit. The best schedule is the one you can follow consistently while eating well, sleeping well, and staying active. If you have a medical condition, take medication, are pregnant, or have a history of disordered eating, talk to your healthcare provider before starting any fasting schedule.