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By Toketemu Ohwovoriole & Samantha Cassetty, Insider
Intermittent fasting is an eating plan that allows you to alternate between eating and fasting on a schedule. It's typically used by people who are trying to lose weight or live an overall healthier lifestyle.
"Intermittent fasting gained popularity because scientists discovered that when animals were given a very low-calorie diet, they lived longer and were healthier. But eating a very low-calorie diet is not realistic for human beings, so fasting was found to be the next best thing," says Michael Crupain, MD, chief medical officer of Sharecare, a digital health company.
Important: Intermittent fasting is not right for everyone. Before you start a restrictive diet plan, check with your doctor to see if it's healthy for you.
For people who are unfamiliar with this eating plan, the prospect of fasting might seem daunting. Luckily, there are many schedule options to choose from.
Here are all the different ways you can fast intermittently to help you decide which option is best for you.
The 16:8 method involves fasting for 16 hours every day and only eating during an 8-hour window. You can eat your regular three meals during these 8 hours.
Be careful not to eat more food than you usually would during the non-fasting hours. Eating too much during the 8 hours in anticipation of the 16 hour fast will be counterintuitive to your goals.
And just keep in mind that, although this is one of the most popular methods of intermittent fasting, some research has cast doubt on its efficacy for weight loss.
The best time to fast: This is a commonly preferred method of intermittent fasting because the bulk of your fasting period will typically happen when you are asleep.
For most people using this method, eating an early dinner and skipping breakfast might be the most effective way to stick to the schedule. Say you ended dinner at 8 pm, your next meal will be an early lunch at 12 pm. You are allowed to drink water or other zero-calorie drinks as you fast.
The 14:10 method is an alternative to the 16:8 method for people who might find fasting for 16 hours difficult. In this case, you would fast for 14 hours and eat your meals during a 10-hour period.
Like with the 16:8 method, you are also allowed to drink water or other zero-calorie drinks during the fast.
The best time to fast: While people most commonly start fasting at 7 or 8 pm, you can start later or earlier than these times. However, starting your fast at 7 or 8 pm is ideal because it typically has you eating your last meal a couple of hours before your bedtime, which gives your body time to digest your food properly before you sleep.
With the 5:2 method, you are required to restrict the number of calories you consume for two days in a week. During the other five days, you can eat normally. On fasting days, it is typically recommended that you eat no more than 400 to 500 calories.
The best time to fast: When using the 5:2 method, you should avoid fasting on two consecutive days. Fasting for two days in a row makes you more susceptible to experiencing side effects like extreme hunger, irritability and fatigue.
As the name suggests, alternate-day fasting requires you to fast every other day. Some people do 24-hour fasts, but this might be overwhelming for people who are just starting. Alternatively, you could restrict your usual calorie consumption on fasting days, to an extent you feel comfortable with.
Alternate-day fasting has become more popular in recent years, but medical experts warn against its potential health risks.
In a small 2017 study, researchers split 100 obese women into three groups. The first group followed an alternate fasting diet that allowed them to eat 25% of the calories they needed on fasting days, and 125% on non-fasting days. The second group restricted their calorie consumption to 75% everyday, and the last group ate as they usually would.
At the end of the year-long study, the researchers observed that women in the first two groups had lost around 5.5% of their body weight by the sixth month of the study.
However, those who did alternate fasting also had significantly higher low-density lipoprotein (LDL) cholesterol levels than those who restricted their daily calories - which indicate a higher risk of dangerous heart conditions like heart attacks and strokes.
For that reason, it's best to consult your doctor before alternate fasting.
The best time to fast: For people who do 24-hour fasts, you might want to take advantage of starting your fast just after dinner. If you start a 24-hour fast at 7 pm, and go to bed for 8 to 9 hours at 10 pm, there'll be only 12 to 13 hours left in your fast by the time you wake up.
However, this method is generally not recommended, so proceed with caution.
The biggest downside of this method is that many people find 24-hour fasts to be difficult to endure. This method might also not be safe for people with certain medical conditions like diabetes or an eating disorder.
You are allowed to drink water and zero-calorie drinks during fast periods. This can help you cope with feelings of hunger. For people who fast for 24 hours, you might experience side effects like headaches, fatigue, and irritability.
The best time to fast: With the eat-stop-eat method you can fast on any day of the week you choose. However, if you fast twice a week, it's advisable to choose two non-consecutive days.
This method is especially great for beginners who aren't sure what intermittent schedule might work best for them. While flexibility might be the biggest advantage of this method, it is also its downside.
"Spontaneous meal skipping may help you reduce calories, but you are likely to overeat afterward. Following a structured eating and fasting schedule is important to help you stay consistent and develop the habits you need to be successful at intermittent fasting," Crupain says.
Intermittent fasting is a risky eating plan for many. People who are pregnant, have had eating disorders, medical conditions like diabetes, and those 65 and older should avoid intermittent fasting.
Overall, if you are considering an intermittent fasting schedule, you should speak to your doctor first to make sure it's the right eating plan for you.
See more at Insider
Intermittent fasting is an eating plan that allows you to alternate between eating and fasting on a schedule. It's typically used by people who are trying to lose weight or live an overall healthier lifestyle.
"Intermittent fasting gained popularity because scientists discovered that when animals were given a very low-calorie diet, they lived longer and were healthier. But eating a very low-calorie diet is not realistic for human beings, so fasting was found to be the next best thing," says Michael Crupain, MD, chief medical officer of Sharecare, a digital health company.
Important: Intermittent fasting is not right for everyone. Before you start a restrictive diet plan, check with your doctor to see if it's healthy for you.
For people who are unfamiliar with this eating plan, the prospect of fasting might seem daunting. Luckily, there are many schedule options to choose from.
Here are all the different ways you can fast intermittently to help you decide which option is best for you.
16:8 method
 |
| A 16:8 intermittent fasting schedule still has 8 hours where you can eat each day. ©Taylor Tyson / Insider |
The 16:8 method involves fasting for 16 hours every day and only eating during an 8-hour window. You can eat your regular three meals during these 8 hours.
Be careful not to eat more food than you usually would during the non-fasting hours. Eating too much during the 8 hours in anticipation of the 16 hour fast will be counterintuitive to your goals.
And just keep in mind that, although this is one of the most popular methods of intermittent fasting, some research has cast doubt on its efficacy for weight loss.
The best time to fast: This is a commonly preferred method of intermittent fasting because the bulk of your fasting period will typically happen when you are asleep.
For most people using this method, eating an early dinner and skipping breakfast might be the most effective way to stick to the schedule. Say you ended dinner at 8 pm, your next meal will be an early lunch at 12 pm. You are allowed to drink water or other zero-calorie drinks as you fast.
14:10 method
 |
| A 14:10 intermittent fasting schedule has 14 hours of fasting per day. ©Taylor Tyson / Insider |
The 14:10 method is an alternative to the 16:8 method for people who might find fasting for 16 hours difficult. In this case, you would fast for 14 hours and eat your meals during a 10-hour period.
Like with the 16:8 method, you are also allowed to drink water or other zero-calorie drinks during the fast.
The best time to fast: While people most commonly start fasting at 7 or 8 pm, you can start later or earlier than these times. However, starting your fast at 7 or 8 pm is ideal because it typically has you eating your last meal a couple of hours before your bedtime, which gives your body time to digest your food properly before you sleep.
5:2 method
 |
| A 5:2 intermittent fasting schedule has two full days of fasting. ©Taylor Tyson / Insider |
With the 5:2 method, you are required to restrict the number of calories you consume for two days in a week. During the other five days, you can eat normally. On fasting days, it is typically recommended that you eat no more than 400 to 500 calories.
The best time to fast: When using the 5:2 method, you should avoid fasting on two consecutive days. Fasting for two days in a row makes you more susceptible to experiencing side effects like extreme hunger, irritability and fatigue.
Alternate day fasting
 |
| An alternate day fasting schedule is difficult and not always recommended. ©Taylor Tyson / Insider |
As the name suggests, alternate-day fasting requires you to fast every other day. Some people do 24-hour fasts, but this might be overwhelming for people who are just starting. Alternatively, you could restrict your usual calorie consumption on fasting days, to an extent you feel comfortable with.
Alternate-day fasting has become more popular in recent years, but medical experts warn against its potential health risks.
In a small 2017 study, researchers split 100 obese women into three groups. The first group followed an alternate fasting diet that allowed them to eat 25% of the calories they needed on fasting days, and 125% on non-fasting days. The second group restricted their calorie consumption to 75% everyday, and the last group ate as they usually would.
At the end of the year-long study, the researchers observed that women in the first two groups had lost around 5.5% of their body weight by the sixth month of the study.
However, those who did alternate fasting also had significantly higher low-density lipoprotein (LDL) cholesterol levels than those who restricted their daily calories - which indicate a higher risk of dangerous heart conditions like heart attacks and strokes.
For that reason, it's best to consult your doctor before alternate fasting.
The best time to fast: For people who do 24-hour fasts, you might want to take advantage of starting your fast just after dinner. If you start a 24-hour fast at 7 pm, and go to bed for 8 to 9 hours at 10 pm, there'll be only 12 to 13 hours left in your fast by the time you wake up.
However, this method is generally not recommended, so proceed with caution.
Eat-stop-eat
This method involves fasting for 24 hours once or twice a week. This means that if you have dinner at 8 pm on a Wednesday your next meal will be at 8 pm on Thursday.The biggest downside of this method is that many people find 24-hour fasts to be difficult to endure. This method might also not be safe for people with certain medical conditions like diabetes or an eating disorder.
You are allowed to drink water and zero-calorie drinks during fast periods. This can help you cope with feelings of hunger. For people who fast for 24 hours, you might experience side effects like headaches, fatigue, and irritability.
The best time to fast: With the eat-stop-eat method you can fast on any day of the week you choose. However, if you fast twice a week, it's advisable to choose two non-consecutive days.
Spontaneous meal skipping
Not all intermittent fasting schedules follow a strict time structure. With spontaneous meal skipping, you can simply skip a meal you don't need to eat from time to time. For example, if you had a big lunch, you might decide to skip dinner.This method is especially great for beginners who aren't sure what intermittent schedule might work best for them. While flexibility might be the biggest advantage of this method, it is also its downside.
"Spontaneous meal skipping may help you reduce calories, but you are likely to overeat afterward. Following a structured eating and fasting schedule is important to help you stay consistent and develop the habits you need to be successful at intermittent fasting," Crupain says.
Insider's takeaway
Starting an intermittent fasting meal plan may seem daunting. Fortunately, there are many different schedules you can try to find the best plan for you.Intermittent fasting is a risky eating plan for many. People who are pregnant, have had eating disorders, medical conditions like diabetes, and those 65 and older should avoid intermittent fasting.
Overall, if you are considering an intermittent fasting schedule, you should speak to your doctor first to make sure it's the right eating plan for you.
See more at Insider
