Which intermittent fasting schedule is best for beginners?

Start with 12/12: a 12-hour overnight fast, often from 7 pm to 7 am, which mostly means cutting out late-night snacks. After one or two comfortable weeks, move to 14/10, then 16/8 if you want to. There is no need to go further: a 14/10 you can keep up is better than a 20/4 you drop after three days.

What time should I eat on 16/8?

There is no required schedule. For most people, a window from 11 am to 7 pm or 10 am to 6 pm works well: you skip breakfast but keep lunch and dinner with the family. If you would rather keep breakfast, 7 am to 3 pm is possible, and finishing early seems to suit sleep better. The tool works out the window from your own wake-up time and bedtime.

What can I drink while fasting? Does coffee break a fast?

Water, plain sparkling water, and tea or coffee without sugar do not break a fast in the usual sense: they have almost no calories. Sugar, condensed milk, sweetened soy milk, milk tea or bubble tea do. A splash of milk in coffee adds a few calories: opinions differ, and for a strict fast you skip it. In hot weather, drink regularly to avoid dehydration.

Does intermittent fasting really help you lose weight?

It can help, mainly because a shorter window often means eating less. But clinical trials have not shown it to beat ordinary calorie reduction when total intake is the same. What you eat inside the window matters as much as the timing. To find out how much you need, use the calorie calculator linked from this tool.

Who should not do intermittent fasting?

Pregnant or breastfeeding women, people with diabetes on insulin or certain tablets (risk of low blood sugar), anyone with a current or past eating disorder, and under-18s. If you take medication with meals, are underweight, have a chronic condition (kidneys, heart, low blood pressure) or are over 65, ask your doctor first.

What is the 5:2 diet?

You eat normally five days a week and, on two non-consecutive days (for example Monday and Thursday), limit your intake to about 500 kcal for women and 600 kcal for men, often as two small meals rich in vegetables and protein. It is a good option if you do not want to change your meal times every day. The tool lets you choose the two days and checks that they are not back to back.

Can I exercise while fasting?

A walk, yoga or moderate exercise usually goes fine. For hard or long training sessions, many people prefer to train during the eating window or just before their first meal. In hot weather, drink more and stop if you feel dizzy, unwell or notice palpitations.

Free

Intermittent fasting planner

Pick a protocol and enter when you wake up and go to bed: the tool places your eating window on a 24-hour clock, tells you whether you are eating or fasting right now, runs a timer and builds your week around Thai street breakfasts and family dinners. Free, no sign-up, and everything stays on your phone.

Free, no sign-up, nothing stored

How it works

Intermittent fasting is about when you eat, not what: you eat within a window of a few hours and only have zero-calorie drinks the rest of the time. "16/8" means 16 hours of fasting and an 8-hour eating window; "OMAD" means one meal a day; "5:2" means five normal days and two non-consecutive days at about 500 kcal for women and 600 kcal for men. The tool places your window based on your wake-up time and bedtime, using two simple rules of thumb: a first meal at least one hour after waking and a last meal about three hours before bed. You can keep breakfast, keep dinner, aim for the middle of the day, or choose the start time yourself.
The ring clock shows the whole 24 hours at a glance: your eating window, the fast, your night's sleep and the current time. It also works out how many fasting hours happen while you sleep: with a well-placed window, half of a 16/8 fast is done in bed. The timer starts when you tap "Start my fast" and is recalculated from that timestamp, so it stays accurate even if you close the page or switch off your phone.
The fasting stages are rough guides, not a precise biological clock. What is well established: after a meal, the body first burns glucose; then insulin falls and the liver draws on its glycogen stores, which shrink over the first day (Rothman et al., Science 1991). Somewhere between 12 and 36 hours depending on the person, the body relies more and more on fat and produces ketone bodies: this is the "metabolic switch" described by Anton et al. (Obesity, 2018). Mild ketosis is therefore possible after 12 to 18 hours, but it depends on your last meal, your activity and your body. What science does not say: there is no reliable measure of autophagy in humans during a 16-hour fast; the figures you see online come mostly from animal studies.
What about weight loss? Clinical trials show that intermittent fasting helps people lose weight mostly because they end up eating less. In the TREAT trial (Lowe et al., JAMA Internal Medicine 2020), 16/8 with no other advice did no better than three regular meals. In a one-year trial published in the New England Journal of Medicine (Liu et al., 2022), adding an 8-hour eating window to calorie restriction did no better than calorie restriction alone. Intermittent fasting remains a practical way to organise meals for people who feel good doing it, as long as what you eat inside the window is balanced: vegetables, protein, a sensible portion of rice and few sugary drinks.
The weekly plan is built for life in Thailand: it flags the days when your window covers a street breakfast (jok, khao tom, khao niao mu ping), office lunch and the family dinner, and can give you more relaxed 12/12 weekends for shared meals. Not eating after noon is nothing new here: it is one of the eight precepts (sila 8) kept by lay people on Buddhist holy days (wan phra), and monks do not eat after noon either; the parallel is cultural, not medical. Ramadan fasting is not covered: it is a religious practice with its own rules (no water from dawn to sunset) that this tool does not calculate.
Safety and sources. The tool shows no plan during pregnancy or breastfeeding, for people with diabetes on treatment (risk of low blood sugar with insulin or some tablets), for anyone with a current or past eating disorder, or for under-18s. It recommends staying on gentle protocols if you take medication with meals, are underweight, have a chronic condition or are over 65. Stages are not shown beyond 24 hours: longer fasts need medical supervision. Sources: de Cabo and Mattson, New England Journal of Medicine 2019; Anton et al., Obesity 2018; Cahill, Annual Review of Nutrition 2006; Rothman et al., Science 1991; Lowe et al., JAMA Internal Medicine 2020; Liu et al., New England Journal of Medicine 2022; Harvie et al., International Journal of Obesity 2011 for 5:2 (that study aimed for about a quarter of energy needs on low days; the 500 and 600 kcal figures come from the popular version). This tool is for information and does not replace advice from a doctor or dietitian.

These tools give general information. They do not replace the advice of a doctor or a qualified professional.

Go furtherNutrition & detox

Frequently asked questions

Which intermittent fasting schedule is best for beginners?: Start with 12/12: a 12-hour overnight fast, often from 7 pm to 7 am, which mostly means cutting out late-night snacks. After one or two comfortable weeks, move to 14/10, then 16/8 if you want to. There is no need to go further: a 14/10 you can keep up is better than a 20/4 you drop after three days.
What time should I eat on 16/8?: There is no required schedule. For most people, a window from 11 am to 7 pm or 10 am to 6 pm works well: you skip breakfast but keep lunch and dinner with the family. If you would rather keep breakfast, 7 am to 3 pm is possible, and finishing early seems to suit sleep better. The tool works out the window from your own wake-up time and bedtime.
What can I drink while fasting? Does coffee break a fast?: Water, plain sparkling water, and tea or coffee without sugar do not break a fast in the usual sense: they have almost no calories. Sugar, condensed milk, sweetened soy milk, milk tea or bubble tea do. A splash of milk in coffee adds a few calories: opinions differ, and for a strict fast you skip it. In hot weather, drink regularly to avoid dehydration.
Does intermittent fasting really help you lose weight?: It can help, mainly because a shorter window often means eating less. But clinical trials have not shown it to beat ordinary calorie reduction when total intake is the same. What you eat inside the window matters as much as the timing. To find out how much you need, use the calorie calculator linked from this tool.
Who should not do intermittent fasting?: Pregnant or breastfeeding women, people with diabetes on insulin or certain tablets (risk of low blood sugar), anyone with a current or past eating disorder, and under-18s. If you take medication with meals, are underweight, have a chronic condition (kidneys, heart, low blood pressure) or are over 65, ask your doctor first.
What is the 5:2 diet?: You eat normally five days a week and, on two non-consecutive days (for example Monday and Thursday), limit your intake to about 500 kcal for women and 600 kcal for men, often as two small meals rich in vegetables and protein. It is a good option if you do not want to change your meal times every day. The tool lets you choose the two days and checks that they are not back to back.
Can I exercise while fasting?: A walk, yoga or moderate exercise usually goes fine. For hard or long training sessions, many people prefer to train during the eating window or just before their first meal. In hot weather, drink more and stop if you feel dizzy, unwell or notice palpitations.

Intermittent fasting planner

Before you start

Your day over 24 hours

Fasting timer

Your progress

What happens while you fast

Your week

What can you drink while fasting?

How it works

Frequently asked questions

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