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18:6 fasting, two hours further.

You don't eat for 18 hours, then you eat for 6. Dinner at 8pm, first meal at 2pm the next day, or dinner at 6pm and lunch at noon.

Those two extra hours take you to the edge of Ketosis Entry, where a 16:8 finishes in Fat Mobilisation. That is the reason to step up to it.

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Burn's timer at 18 hours 47 minutes on an 18:6 fast, the stage pill reading KETOSIS, with a stage progress rail at 3h, 8h, 14h, 18h and 24h and a Ketones Rising card

One day on an 18:6

Dinner ends 6pm, first meal noon

6pm-9pmStill digesting

9pm-2amAsleep for this part

2am-8amWaking into the hungry stretch

8am-noonFat release

noon-6pmEating window, two meals

An 18-hour fast ends exactly at the Ketosis Entry boundary. Run a little past your goal and you are into the stage itself.

What the extra two hours change

You reach the Ketosis Entry line

A 16:8 finishes mid Fat Mobilisation. An 18:6 runs to the boundary of the next stage, where ketone production becomes meaningful.

Lunch moves, or dinner does

Six hours fits two meals rather than three. The two workable shapes are pushing lunch to mid-afternoon, or eating dinner early.

Hunger arrives earlier in the day

The hard window is the same one, around hour 14, but on an 18:6 you still have four hours to go when you reach it.

16:8 or 18:6

Two hours apart, side by side

Same day, same timer, two different finishing points.

Ketosis Entry appears as KETOSIS on the timer screen, where space is tight. Same stage, shorter name.

16:8

Finishes in Fat Mobilisation. Eight hours of eating covers lunch and dinner, so most plans still work.

Reaches: Fat Mobilisation

The 16:8 guide →

Burn's timer at 16 hours 22 minutes with the 16:8 goal met

18:6

Runs to the Ketosis Entry boundary. Six hours of eating means two meals, and usually one of them moves.

Reaches: Ketosis Entry at 18h

What happens at 18 hours →

Pick your window

Six hours, three ways to place them

The window you can hold on a Saturday matters more than which hours you pick.

11am - 5pm

Early window

A late breakfast and an early dinner. Suits anyone who sleeps badly after eating.

Hardest part: dinner invitations.

2pm - 8pm

Standard

Late lunch window

Skip breakfast, push lunch to mid-afternoon, keep dinner where it is.

Hardest part: hours 12 to 16, late morning.

noon - 6pm

Early dinner window

Lunch at the usual time and dinner brought forward. Good if you train in the morning.

Hardest part: eating dinner before six.

Stepping up to it

Arrive at 18:6, don't jump to it

Hold a 16:8 first

If 16 hours still feels like work, 18 will feel like a fight. Get the shorter one boring first.

Add the hours to the front

Finishing dinner earlier is easier than pushing lunch later, and it puts more of the fast into your sleep.

Watch what you eat in six hours

Two meals in a shorter window makes under-eating easier to do by accident. Eat properly when the window opens.

Keep some days at 16:8

A weekday 18:6 with easier weekends is a schedule people keep. Seven perfect days is not.

Read: how to make fasting easier →

Burn's timer at 14 hours 36 minutes, shown on the timer as Fat Release

Burn's home screen with a hunger timer counting down from 19 minutes 38 seconds above the End Fast button

What the evidence supports

Longer is not automatically better

Time-restricted eating is one of the better studied approaches to eating patterns. What is less established is whether 18 hours beats 16.

Well supported

01Shorter eating windows tend to reduce total intake without counting anything.
02Ketone levels rise as a fast lengthens, and can be measured with a blood or breath test.
03Adherence matters more than the specific window for results over months.

Where research continues

01Head to head trials of 18:6 against 16:8 with total intake matched.
02Whether the added ketone rise translates into outcomes people notice.
03How window placement interacts with sleep and training.

Burn tracks elapsed time and names the stage that time corresponds to. It does not measure ketones or anything else happening in your cells. If you are pregnant or breastfeeding, have a history of disordered eating, manage diabetes, or take medication timed with food, speak to a clinician before starting.

Try it on a weekday first

Burn holds the window, names each stage as you cross it, and has the support tools ready for the hours that are hard.

Download free on the App Store

iPhone, iPad, and Apple Watch. Requires iOS 18 or watchOS 11.