Every intermittent fasting protocol is just a different answer to one question: how long is the eating window? 16:8 gives you eight hours. 18:6 gives you six. OMAD gives you about one. Here’s what each trades, and how to pick the one you’ll actually do.
16:8 — the default
A 16-hour fast with an 8-hour eating window is the most popular IF protocol for a reason: you sleep through most of it. Stop eating at 8pm, skip breakfast, eat lunch at noon. That’s the whole thing.
Who it’s for: beginners, people who hate breakfast anyway, anyone who wants a simple calorie-limiting ritual without counting. You fit two real meals plus a snack into the window without stress.
What it costs: a little social friction at breakfast meetings or early brunches. That’s it.
18:6 — the step up
An 18-hour fast with a 6-hour eating window is the natural progression. Eat from 1pm to 7pm, or noon to 6pm. You’re still fitting two meals in — they just have to sit closer together.
Who it’s for: experienced fasters who plateaued at 16:8 and want slightly more deficit without cutting calories further. Also people who naturally eat one bigger late lunch and an early dinner.
What it costs: dinner-hour flexibility. Social dinners past 7pm require rescheduling your window. Some people find the hunger spike around hour 16 harder at 18:6 than at 16:8.
Pick a protocol, set your break-fast time. See exactly which hours are fasting and which are feeding.
OMAD — one meal a day
OMAD compresses eating into a single meal — usually a 1-to-2-hour window. It’s extreme, and it works for the same reason extreme diets always work: it’s very hard to eat a surplus in an hour.
Who it’s for: experienced fasters who want maximum compliance simplicity (one meal is easy to plan), people whose schedule only permits one meal, or short-term cuts. Not a long-term lifestyle for most people.
What it costs: protein intake, realistically. Hitting 150g of protein in one meal is a logistical challenge. Social eating becomes hard. Training output suffers for most people until they adapt (weeks, not days).
How to actually pick
The best protocol is the one you’ll still be doing in six months. Start at 16:8. If it’s trivial after a month and the scale has stalled, tighten to 18:6. Only consider OMAD if you have a specific goal with a specific end date.
A few rules that apply to every window:
- Protein first, always. Hit your daily grams inside the window. Everything else is secondary.
- Water, salt, caffeine are free. None of them break a fast. Coffee is what makes the morning work.
- Don’t binge when the window opens. Break the fast with a normal meal, not a 2,000-calorie blowout. The window is a boundary, not a license.
- Track calories at least the first two weeks. IF doesn’t create a deficit by itself; it just makes one easier to hit.
The honest summary
IF isn’t magic and it isn’t cheating. It’s a scheduling tool that makes calorie restriction easier for some people and harder for others. If you struggle with evening snacking, a window helps. If you train hard in the morning and need fuel, a long morning fast will kneecap you. Pick the protocol that matches your life, not the one that sounds most impressive on Reddit.
Every protocol, rendered on a 24-hour timeline. Share the URL and schedule around it.