HOME / FASTING / 18:6 VS OMAD

18:6 or OMAD

Both reach Ketosis Entry, 18:6 at its opening and OMAD five hours in. One gives you six hours to eat in, the other about one, and that is where the decision actually sits.

Here is what the extra five hours buy you, and what they cost.

18:6

ENDS AT THE KETOSIS ENTRY LINE

Eighteen hours fasting, six to eat

Two meals in six hours, usually a late lunch and a dinner. The fast ends exactly where Ketosis Entry opens, so running a little past your goal puts you inside the stage itself.

Meals Two, without rushing

Eating window Six hours

Hard hour Around 14, before the end

Stage reached Ketosis Entry, at its start

The 18:6 guide →

OMAD

ENDS INSIDE KETOSIS ENTRY

One meal a day, one hour to eat it

Roughly 23 hours fasting and a single sitting. Five hours further into the same stage, with the whole day's food in one meal and the window fixed to one hour of the evening.

Meals One, large

Eating window About one hour

Hard hour Around 14, then it eases

Stage reached Ketosis Entry, five hours in

The OMAD guide →

One stage, five hours apart

18:6 at the boundary, OMAD an hour short of Fat Burning

0-3hFed State

3-8hEarly Fasting

8-14hGlycogen Depletion

14-18hFat Mobilisation

18-24hKetosis Entry

24-48hFat Burning

Both reach Ketosis Entry, the stage where ketone production becomes meaningful and hunger often drops. Neither reaches Fat Burning, which does not open until 24 hours. The five hours between them are spent inside one stage, not crossing into a new one.

Where they differ

Six hours is a window. One hour is an appointment.

Since the stage is the same, everything that separates these two is about the eating side rather than the fasting side.

EATING

Two meals or one

Six hours holds two proper meals and makes protein straightforward. A single sitting has to carry the whole day, and that takes planning rather than willpower.

FLEXIBILITY

A dinner that moves

Six hours absorbs a meal pushed back an hour or two. One hour does not, so OMAD asks for a week where your evenings are reliably yours.

TRAINING

Room either side of a session

Hard efforts want glycogen. Six hours gives you somewhere to put a session with food before and after it, which one hour cannot.

Choosing

Which one to pick

Pick 18:6 if you want two meals

It reaches the same stage as OMAD with a window that fits a normal evening. For most of what people want from a long daily fast, this is the version that survives a busy week.

Pick OMAD if one decision is simpler than three

Some people find a single meal easier to plan and easier to stop thinking about. If you like large meals and your evenings are predictable, the clock is not the difficult part.

Try 20:4 in between

Four hours is still one window but leaves room for a meal and something after it. It is the honest middle step, and switching plans keeps your history intact.

The 20:4 guide → Every daily schedule →

Burn's timer at 18 hours 47 minutes on an 18:6 fast, the stage pill reading KETOSIS

Burn's timer at 20 hours 9 minutes, the stage pill reading KETOSIS, the stage an OMAD fast finishes in

What the evidence supports

Time-restricted eating produces weight loss in controlled human trials, comparable to other approaches at matched intake. No trial establishes that a one hour window outperforms a six hour one. Which pattern a person can sustain matters more than which is theoretically optimal. Claims here are drawn from peer-reviewed research and traced in our evidence policy.

Before you start either

Speak to your doctor first if you are pregnant or breastfeeding, have a history of eating disorders, manage diabetes, take medication timed to meals, or are under 18. A one meal a day pattern makes it harder to meet your needs, so it deserves that conversation more than a six hour window does.

Run either one, and see the stage arrive

Both are built into Burn, and switching between them keeps every fast you have already logged.

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