18:6 intermittent fasting schedule

18:6 intermittent fasting stretches the overnight gap to 18 hours and fits the day’s eating into six. It is the next step up from 16:8, for people who want to drop one more snack or an early meal. Set your last meal below to see when your next 6-hour window opens.

Sample 18:6 schedules with clock times

The window opens 18 hours after you finish eating and closes 6 hours later. Here are four common placements.

Eating window	Last bite by	Next window opens	Good for
9 am to 3 pm	3 pm	9 am	Early risers who like breakfast and can skip dinner
12 pm to 6 pm	6 pm	12 pm	Lunch plus an early dinner
1 pm to 7 pm	7 pm	1 pm	A late lunch and a family dinner
2 pm to 8 pm	8 pm	2 pm	Late evenings and social meals

Our schedule chooser uses three of these. Morning eaters get 9 am to 3 pm, midday eaters 12 pm to 6 pm, and evening eaters 2 pm to 8 pm.

Here is one day on the 1 pm to 7 pm window:

• 1:00 pm: first meal, built around a protein food such as eggs, fish, tofu or beans.
• 4:00 pm: optional snack.
• 6:15 pm: second meal, eaten by 7 pm.
• 7 pm until 1 pm the next day: no food; drink water, black coffee or plain tea.

What trials of 18:6 intermittent fasting found

Three studies tested 18 hours of daily fasting with a 6-hour window. All were small or short.

Window	Who and how long	What happened
1 pm to 7 pm	Adults with obesity, 8 weeks	About 3% weight loss, the same as a 4-hour window. Both groups cut about 550 kcal a day without counting, against a group with no time limit
6 hours, dinner before 3 pm	8 men with prediabetes, 5 weeks on each schedule, fed enough to keep their weight steady	Better insulin sensitivity and lower blood pressure than on a 12-hour schedule. Morning systolic pressure fell by about 11 mm Hg
8 am to 2 pm	11 adults with overweight, 4 days	Compared with eating from 8 am to 8 pm, average 24-hour blood sugar was about 4 mg/dl lower; ketones rose

In the prediabetes study, the men did not lose weight, because they were fed to keep it steady, yet some measures still improved. That suggests meal timing may matter a little on top of eating less. With only 8 people for 5 weeks, the evidence is early.

The weight-loss result is early evidence as well, from one 8-week trial. None ran longer than 8 weeks, none compared 18:6 with 16:8 directly, and none was designed to show fewer heart attacks or less diabetes. For results over a full year, the evidence comes from 8-hour windows, covered on the 16:8 page.

Does 18:6 reach ketosis or autophagy?

In human studies, the body turns to fat and starts making ketones somewhere between 12 and 36 hours without food. An 18-hour fast sits inside that range, so some days you will get there and some days you won’t. Your last meal and your activity that day decide which.

In the 4-day study above, the early window raised ketones and the activity of one autophagy-related gene (LC3A). That gene marker was measured in blood, so it is not a measurement of autophagy itself. No human study has shown the hour when autophagy starts, so 18:6 can’t promise it.

Who 18:6 suits, and who should skip it

18:6 works best for people who already find 16:8 easy and are happy eating twice a day. Our chooser keeps it for regular fasters, meaning 14 hours or more already, who eat two meals or fewer.

It leaves less time than 16:8 to eat enough. Fitting protein into two meals is the main challenge. Take an active 80 kg (176 lb) adult. The protein range for people who exercise is 1.4 to 2.0 g for each kilogram daily. That makes 112 to 160 g, or about 56 to 80 g in each of two meals. People over 65 need at least 1.0 to 1.2 g per kg every day.

Ask a doctor before trying 18:6 if you are pregnant, breastfeeding or under 18. Do the same with type 1 diabetes, or a prescription for insulin or a sulfonylurea. Those two medicines can drop blood sugar too far over an 18-hour gap. Our advice is against 18:6 for anyone underweight or with a past or current eating disorder.

Stepping up from 16:8, and back down

Move up in one-hour steps. From a 12 pm to 8 pm window on 16:8, start eating at 1 pm for a week, which gives 17:7. Then either start at 2 pm or finish your last meal an hour earlier.

If 18 hours feels like too much, return to 16:8 and stay there. A schedule you can keep matters more than the extra two hours. If you want to go further, the 20:4 schedule is the next step, and it is more demanding still.

A realistic first week on 18:6

This week assumes you are already comfortable on 16:8 and finish dinner at 7 pm. Treat it as our suggestion, not a rule.

Day	First meal	Hours fasted	Focus
1 to 3	12 pm	17	Two full meals, with protein in both
4 to 5	1 pm	18	Drink water through the late morning
6	1 pm	18	Check you finished eating by 7 pm
7	1 pm, or 12 pm on a busy day	17 to 18	Notice sleep, energy and hunger

If your periods change, your sleep suffers, or the second meal becomes a binge, go back to 16:8. The 16:8 vs 18:6 vs OMAD guide compares the daily windows. Every option sits in one table on our intermittent fasting schedules hub. To track each 18-hour fast, use the fasting timer, which runs offline and keeps your history on your device.