Quick Answer: The five common intermittent fasting schedules are 12:12, 14:10, 16:8, 18:6 and 5:2. They differ mainly in how much of your normal eating pattern they disrupt: 12:12 and 14:10 usually require no meals to be dropped, 16:8 removes one, 18:6 compresses everything into two meals, and 5:2 keeps normal eating five days a week with two very low-calorie days. The best schedule is the one that fits your fixed obligations — work hours, family meals, training time — not the most aggressive one you can tolerate.

Every fasting article starts by explaining what 16:8 means and then stops, which leaves out the only question that matters: which of these will still be running in six weeks given the actual shape of your week.

Here they are side by side, with the failure mode for each — because the failure modes are more useful than the descriptions.

What does each intermittent fasting schedule actually mean?

All of the time-restricted schedules use the same notation: hours fasting to hours eating. The fasting hours include your sleep, which is why the numbers look more dramatic than they are.

12:12 — a twelve-hour eating window, for example 8am to 8pm. This is close to how most people already eat, minus late-night snacking. It is the version most often recommended as a starting point and the one most often dismissed as not counting.

14:10 — a ten-hour window, say 9am to 7pm. Usually achieved by pushing breakfast slightly later and closing the kitchen after dinner. Almost nobody has to skip a meal to do this.

16:8 — an eight-hour window, commonly 12pm to 8pm. This is the popular one. In practice it means skipping breakfast or skipping dinner, and which one you skip changes almost everything about how it feels.

18:6 — a six-hour window, perhaps 1pm to 7pm. Two substantial meals, or one meal and a large snack. Meaningfully harder to hit protein and fiber targets in.

5:2 — a different structure entirely. Five days of normal eating and two non-consecutive days at roughly a quarter of usual intake. No daily window at all.

A sixth worth knowing: early time-restricted eating, which is any of the above shifted early — for example 8am to 4pm. The evidence on metabolic markers is somewhat more favorable for early windows than late ones, and it is socially the hardest version to sustain because it removes dinner.

How do the five compare on the things that actually decide it?

Difficulty in the first two weeks. 12:12 is nearly frictionless. 14:10 is mild. 16:8 produces a genuine adjustment period of roughly one to two weeks, usually including headaches around day two. 18:6 is harder again. 5:2 is easy five days a week and genuinely unpleasant on the other two, which is a very different distribution of difficulty and suits some people far better.

Compatibility with a normal job. 16:8 with a noon-to-eight window fits a standard office day almost perfectly. 16:8 with an early window does not, because it kills dinner. 5:2 fits any schedule but requires you to get through two working days on very little, which is fine for desk work and rough for anything physical.

Compatibility with family meals. This is the criterion that decides it for most people and is almost never listed. If dinner with other people is non-negotiable, every late-window schedule works and every early-window schedule fails. If breakfast with children is the fixed point, the reverse.

Compatibility with training. Fasted training is fine for easy sessions and generally worse for hard ones. If you train at six in the morning, an eating window that starts at noon means training fasted and then waiting six hours to refuel, which is the single most common reason people abandon 16:8. Either shift the window or shift the session.

Nutritional adequacy. The shorter the window, the harder it is to eat enough protein and fiber. At 18:6 most people need to plan this deliberately. At 5:2 the fasting days are nutritionally thin by design and the other five have to carry the week.

Social durability. 12:12 and 14:10 survive holidays, dinners and weekends without a thought. 18:6 does not, and the reported drop-off is correspondingly higher.

Which schedule fits which kind of week?

If your week is unpredictable — shifts, travel, on-call: 12:12 or 14:10. A schedule that survives disruption beats a stricter one that collapses every time the week changes. This is also the right answer for anyone who has tried and abandoned 16:8 twice.

If you have a fixed office day and eat dinner with people: 16:8 with a noon-to-eight window. This is the default recommendation for good reason — it removes one meal, the one that is easiest to remove, and touches nothing else.

If you are an early riser who trains in the morning and eats early: early time-restricted eating, 8am to 4pm or 9am to 5pm. Best evidence, worst social fit. Works well for people who live alone or whose household eats early.

If your problem is evening grazing rather than meals: 12:12, strictly enforced. The mechanism here is not the fasting, it is that a closing time removes the three hundred to six hundred calories that were arriving between nine and eleven at night without being noticed.

If you strongly prefer a normal day to a restricted one: 5:2. People who hate a daily rule and are fine with an occasional hard day consistently do better on this than on anything with a window.

If you are trying to do a lot of hard training: honestly, none of them, or 12:12. Compressed windows and high training volume conflict on both fueling and recovery, and the fasting is the part to compromise.

A note on timing shifts: everything above is harder in the last week of August than it was in July. Later sunrises change hunger timing, the school calendar moves meals, and windows that worked all summer start drifting. Reset the window deliberately rather than letting it slip.

Myth vs Fact: Fasting Schedules

Myth: A longer fast is always better. Fact: The evidence for time-restricted eating largely shows benefits that plateau rather than scale — most of the measurable improvement in the research shows up in the move from unrestricted eating to a defined window, not in the move from 16:8 to 18:6. What does scale with a longer fast is dropout.

Myth: 12:12 is not real fasting. Fact: It is the version with the highest long-term adherence and it eliminates late-night eating, which for many people is the actual problem. A schedule you keep for two years beats one you keep for five weeks.

Myth: You must skip breakfast. Fact: The window can go anywhere. Skipping dinner produces the same window length and, on the metabolic markers studied, tends to look slightly better. It is skipped less often because it is socially harder, not because it works worse.

Myth: Black coffee breaks the fast. Fact: Black coffee, plain tea and water do not meaningfully affect the mechanisms most people are fasting for. What does is anything with calories, and the milk and sweetener people add without counting.

Myth: The schedule is what produces results. Fact: In the controlled comparisons, time-restricted eating produces outcomes roughly equivalent to conventional calorie restriction. The window is a tool for eating less without counting, and for most people that is exactly what makes it useful.

FAQ: Fasting Schedule Questions, Answered

How long before I should switch schedules if one is not working?

Give any schedule three to four weeks before judging it, because the first two are dominated by adaptation. Switch earlier only if it is actively interfering with sleep, training or work — those are not adaptation, they are a mismatch.

Can I use different schedules on different days?

Yes, and most people who sustain this long term end up doing exactly that: a tighter window on structured weekdays, a looser one at weekends. It is worth planning that rather than treating the weekend as a failure.

Which schedule is best for women specifically?

The honest answer is that the research is thinner than the confident advice around it suggests. What is reasonably well supported: hunger, sleep and cycle-related symptoms are worth tracking, and if a shorter window is coinciding with poor sleep or disrupted cycles, that is a signal to widen it rather than push through.

Who should not do this at all?

Anyone pregnant or breastfeeding, anyone with a history of disordered eating, anyone on medication requiring food, and anyone with diabetes managing it with insulin or sulfonylureas without medical supervision.

This is general information, not medical advice. Talk to a doctor before starting a fasting schedule, particularly if you take regular medication.

TL;DR:

• The five schedules differ mainly in how much of your existing meal pattern they disrupt: 12:12 and 14:10 disrupt almost none, 16:8 removes a meal, 18:6 compresses to two, 5:2 restructures the week.
• Choose by your fixed obligations — work hours, family dinners, training time — not by which is strictest.
• Benefits in the research plateau; dropout does not. A sustainable window beats an ambitious one.
• Late-window schedules survive social life; early-window schedules have slightly better evidence and much worse social fit.
• Give any schedule three to four weeks before judging, and re-set the window when the season shifts your day.

If you have failed at 16:8 more than once, the useful move is not to try harder — it is to run 14:10 properly for a month and see whether the thing you actually needed was a closing time.