Fasting · 3 min read
16:8 vs 18:6 vs 20:4 vs OMAD: Which One People Actually Keep
Try it: Fasting Window Planner — Get a full-day schedule that puts your eating window where your training actually is.
Every protocol comparison ranks these by how much weight you lose. That is the wrong axis. The one that matters is how many people are still running it in month three.
The trade that defines all of them
Longer fast, shorter window. Shorter window, fewer meals. Fewer meals, less total food for most people without counting anything — and also a harder schedule to keep, a harder protein target to hit, and a tighter fit around family meals and work.
The aggressive protocols produce faster short-term change and are abandoned sooner. The gentle ones produce slower change and are still running when the aggressive ones have stopped. Over a year, slower and still running wins comfortably.
14:10 — the version that is barely a protocol
Stop eating at 8 p.m., eat again at 10 a.m. For a lot of people this is roughly what they already do, minus the evening snacking. That is precisely why it works: it removes the single highest-calorie, lowest-satisfaction eating occasion of the day without demanding anything else.
Best for: anyone who has never fasted, anyone whose main problem is eating after dinner, anyone with a family evening meal they will not move.
16:8 — the default for good reasons
Eight hours to eat is enough for two full meals and a snack, which means protein targets are reachable and social meals survive. It is the protocol most people can describe to their family without an argument.
Best for: most people, most of the time. If you are unsure which to pick, pick this one and give it eight weeks before considering anything more aggressive.
18:6 — the first real step up
Six hours is two meals, comfortably, and not much more. The additional two hours of fasting past 16:8 delivers a modest additional benefit and a noticeably harder schedule — the window usually has to sit in the afternoon and evening, which starts to conflict with morning training and with breakfast as a social event.
Best for: people who have run 16:8 for at least a month and want to tighten it. Not a starting point.
20:4 — advanced, and the protein problem appears
Four hours is realistically two meals close together. This is where hitting a protein target of 150 grams or more stops being automatic and starts requiring planning. It is also where sessions scheduled outside the window become genuinely awkward.
Best for: experienced fasters with simple schedules and modest training loads. Poor fit for anyone lifting heavy four or more times a week.
OMAD — highest short-term change, lowest survival rate
One meal a day produces the fastest weight change of the group and the shortest average run. The reasons are predictable: a single meal large enough to carry a day's protein and energy is genuinely uncomfortable, social eating becomes nearly impossible, and the psychological pressure on that one meal is high.
Best for: short defined blocks, or people whose schedule genuinely suits it. Not a long-term default, and not a first protocol.
5:2 — a different mechanism entirely
Eat normally five days, restrict heavily on two non-consecutive days. This works through a weekly deficit rather than a daily window, so it fits people whose days are too unpredictable for a fixed window. The trade-off is that the two restricted days are genuinely hard rather than mildly inconvenient.
How to actually choose
Ask three questions and let the answers decide.
- When do you train? Early morning training and a late window are a bad pair. See fitting the window around training.
- What is your protein target? Over about 150 grams, a four-hour window is a real constraint. Check with the protein calculator before committing.
- What meal is non-negotiable socially? If it is family dinner, the window ends late and everything else arranges around that.
The upgrade path
Start one step easier than you think you need. Hold it for four weeks without a missed day. Then, and only then, consider tightening by two hours. Most people who go straight to 20:4 are back to eating whenever within a month, which leaves them worse off than if they had run 16:8 the whole time.
The fasting window planner will lay out any of these against your actual training time, including whether the session lands somewhere sensible.
Questions I get asked
Which protocol burns the most fat?
Over weeks, the one that produces the largest sustained energy deficit — which for most people is the one they keep doing, not the strictest one.
Can I change protocols day to day?
You can, but a consistent window is where most of the practical benefit comes from. Hunger settles into a schedule it can predict.
Read next
- How to Pick a Fasting Window That Fits Your Training Your fasting window and your training slot have to share the same day. Here is how to arrange them so neither one wrecks the other.
- Hitting Your Protein Target on a Short Eating Window A four or six hour window and a 180 gram target do not automatically fit together. Here is how to make them fit, and when to widen the window instead.
- How to Break a Fast Without Undoing the Day The meal that ends your fast sets up everything that follows it. Here is how to build it so the rest of the window stays under control.