Intermittent Fasting for Beginners
Intermittent fasting is an eating pattern that alternates between periods when you eat and periods when you do not eat. Unlike many diets, the main focus is when you eat, rather than following one specific list of foods.
For beginners, the hardest part is often understanding the basic terms: fasting window, eating window, fasting schedule, and fasting method. Once those are clear, setting up a schedule becomes much simpler.
This guide explains how intermittent fasting works as a scheduling approach, the common methods you may come across, and how to choose a schedule that fits your routine.
What Is Intermittent Fasting?
Intermittent fasting is a pattern of alternating between eating periods and fasting periods.
One common form is time-restricted eating, where food is consumed within a set number of hours each day and the remaining hours make up the fasting period. Other approaches use different schedules, such as alternate-day fasting or the 5:2 pattern.
For example, someone following a 16:8 schedule might have:
- 16 hours of fasting
- 8 hours of eating
The exact clock times depend on when the person's eating window begins and ends.
How Do Fasting and Eating Windows Work?
Two terms are important when building an intermittent fasting schedule.
Fasting window
The fasting window is the period between the end of one eating period and the beginning of the next.
For example, if your last meal ends at 8:00 PM and your next eating period begins at 12:00 PM the following day, the fasting window runs from 8:00 PM to 12:00 PM.
Eating window
The eating window is the period during which your planned meals and snacks fit into your daily schedule.
In a 16:8 pattern, the eating window lasts 8 hours while the remaining 16 hours make up the fasting period.
Thinking in terms of windows can make an intermittent fasting schedule much easier to understand than thinking only in terms of individual meals.
Common Intermittent Fasting Schedules
There is no single intermittent fasting schedule used by everyone. Different methods divide the day or week in different ways.
12:12
A 12:12 schedule divides the day into:
- 12 hours fasting
- 12 hours eating
This creates an even daily schedule and can be easy to visualize.
14:10
A 14:10 schedule uses:
- 14 hours fasting
- 10 hours eating
It provides a longer fasting window while keeping a relatively broad eating period.
16:8
Most PopularThe 16:8 intermittent fasting schedule consists of:
- 16 hours fasting
- 8 hours eating
For example, an eating window from 12:00 PM to 8:00 PM would be followed by a fasting window from 8:00 PM until 12:00 PM the next day.
18:6
An 18:6 schedule divides the day into:
- 18 hours fasting
- 6 hours eating
The eating period is shorter than in a 16:8 schedule, so the clock times should be planned carefully around your normal routine.
20:4
A 20:4 schedule provides:
- 20 hours fasting
- 4 hours eating
This is a substantially narrower eating window than 16:8 or 18:6.
OMAD
OMAD, short for one meal a day, is a different way of structuring a daily fasting schedule around one main meal.
The exact timing can vary, but the basic concept is that the day's food intake is concentrated into a single eating period.
5:2
The 5:2 pattern works differently from daily time-restricted schedules.
Instead of assigning the same fasting window to every day, the pattern divides the week into five regular eating days and two days with restricted calorie intake.
Because it is a weekly pattern, it should not be calculated in the same way as a 16:8 or 18:6 daily schedule.
How to Start Intermittent Fasting
If you are new to intermittent fasting, start by understanding the schedule rather than trying to make it complicated.
1Choose a fasting method
First decide which type of schedule you want to understand or try.
For a daily schedule, this could be 12:12, 14:10, 16:8, 18:6, or another time-based method.
2Pick your fasting start time
Your fasting window normally begins when your eating period ends.
For example: Last meal ends at 8:00 PM → fasting begins at 8:00 PM
This is why your normal dinner time can be useful when planning a schedule.
3Calculate the next eating time
Add the chosen fasting duration to your fasting start time.
For a 16-hour fast beginning at 8:00 PM: 8:00 PM + 16 hours = 12:00 PM the next day
Your eating window would then begin at 12:00 PM.
4Consider your normal routine
A schedule is easier to understand when it fits around your usual day.
Consider:
- your normal breakfast and dinner times
- work or school hours
- sleep schedule
- social meals
- weekends
- your preferred meal timing
The goal of a calculator is to handle the time arithmetic for you, so you can focus on the schedule itself.
How to Choose a Fasting Window
There is no universal clock time that everyone needs to use.
Two people can follow the same fasting method while using different clock times.
For example, both schedules below are 16:8:
12:00 PM → 8:00 PM eating
8:00 PM → 12:00 PM fasting
10:00 AM → 6:00 PM eating
6:00 PM → 10:00 AM fasting
The duration is the same; only the clock times change.
This is why a fasting schedule should be considered in terms of duration and timing, rather than simply copying someone else's meal times.
What Can You Drink During a Fast?
Questions about drinks are common when people begin learning about intermittent fasting.
Water is commonly used during fasting periods. Some guidance also discusses calorie-free drinks such as plain tea or black coffee when describing time-restricted eating.
However, the exact rules people use can vary depending on the fasting approach and the purpose of the fast.
For specific questions such as whether a particular drink or ingredient fits within a fasting period, it is better to look at the ingredients and the rules of the fasting method rather than assuming every drink is treated identically.
Does Intermittent Fasting Mean You Cannot Eat Every Day?
No.
Many popular forms of intermittent fasting are daily schedules in which the fasting and eating windows repeat each day.
For example, a 16:8 schedule can involve eating every day during an 8-hour window and fasting during the remaining 16 hours.
Other methods, such as 5:2 and alternate-day fasting, use different patterns across the week.
How Can a Fasting Calculator Help?
A fasting calculator is mainly a scheduling tool.
Instead of manually calculating when a fasting period ends, you can enter your fasting method and starting time and let the calculator determine the corresponding eating and fasting windows.
For example:
produces:
Fasting: 8:00 PM → 12:00 PM
Eating: 12:00 PM → 8:00 PM
FastTrack's calculator is designed around this type of time calculation.
Common Beginner Questions
What is the easiest fasting schedule to understand?
Daily time-based schedules such as 12:12, 14:10, and 16:8 are straightforward because the same fasting and eating windows repeat each day.
What is a fasting window?
A fasting window is the period in your schedule when you are not eating.
What is an eating window?
An eating window is the planned period during which your meals and other food intake occur.
Can the same fasting schedule have different start times?
Yes. A 16:8 schedule can start at different times while keeping the same 16-hour fasting and 8-hour eating durations.
Is intermittent fasting the same as calorie restriction?
No. They describe different concepts. Intermittent fasting primarily organizes when food is consumed, while calorie restriction focuses on reducing overall calorie intake.
Is intermittent fasting suitable for everyone?
Not necessarily. Intermittent fasting is not appropriate for everyone, and individual circumstances can matter. When appropriate, consider discussing it with a healthcare professional.
Key Takeaways
Intermittent fasting is primarily a way of organizing eating and fasting periods.
The basic concepts are simple:
- Fasting window = time without eating
- Eating window = planned period for eating
- Fasting schedule = the timing pattern that connects the two
- Fasting method = the particular structure, such as 16:8 or 5:2
Daily schedules such as 12:12, 14:10, 16:8, 18:6, and 20:4 use fixed daily fasting and eating durations, while methods such as 5:2 use a weekly structure.
The research around intermittent fasting continues to develop, particularly regarding long-term effects, so it is useful to separate the schedule itself from claims about specific health outcomes.
If you want to calculate a specific fasting and eating window, use the FastTrack Fasting Calculator to turn your chosen method and start time into a daily schedule.