What Is Intermittent Fasting? How Is It Done?

Intermittent fasting is one of the eating patterns that has been widely used in recent years. It is based on dividing the day into a fasting period and an eating period. Some people who want to manage their weight and look after their health choose this pattern, but it does not suit everyone.

You can also take a look at our article "Frequently Asked Questions About Intermittent Fasting" for more detailed information on this way of eating.

What Is Intermittent Fasting?

Intermittent fasting is an eating pattern commonly made up of 2 meals a day, a breakfast and a dinner. It is based on eating at certain hours of the day and not eating anything during the remaining time.

There are 5 different types, so people can choose the one that suits them best. Thanks to these alternatives, the intermittent fasting diet has attracted a lot of interest.

Eating times are called eating windows. Outside of eating windows, only calorie-free fluids such as water, plain soda, and unsweetened coffee or tea are consumed.

Intermittent fasting is an eating pattern that some people choose to follow over the long term. It aims to accustom the body to going without food between meals and to avoid unnecessary carbohydrate intake.

How Is Intermittent Fasting Done?

Intermittent fasting allows you to eat the foods you wish at the set meals. However, it is better to choose healthy foods, so foods high in carbohydrate and sugar, and processed and ready-made foods, are best limited.

There are 5 types of intermittent fasting, so how it is done varies. Whatever the type, the foods you choose should be healthy.

The types of intermittent fasting are as follows:

• The 16:8 method: The 16:8 pattern is the most commonly chosen and best known. It involves a 16-hour fasting window and an 8-hour eating window. In this method the first meal is generally eaten around midday. The fast begins after dinner, towards the end of the 8th hour.
• The Eat-Stop-Eat method: This type of intermittent fasting is done 1 or 2 times a week on days that do not need to be consecutive. It is a 24-hour fast. On the other days people continue their normal eating.
• The modified fasting method: In this method you eat normally on 5 days of the week and follow a calorie-restricted pattern on 2 days. On the planned fasting days, about 20-25% of the usual calories (roughly 500-600 kcal) are eaten. The 2 days are meant to be consecutive.
• The alternate-day method: The alternate-day intermittent fasting method involves eating about 20-25% of the daily calorie need on fasting days. It is the advanced level of intermittent fasting. People fast for one day and eat normally for the next. This pattern is not suitable for beginners or for people with certain health conditions.
• The 12-hour method: More suitable for people new to intermittent fasting. It divides the day in half, with 12 hours of fasting and 12 hours of eating. It can make the process of getting used to the principle of intermittent fasting, and of moving to a lower-calorie way of eating, easier.

What Are Its Reported Benefits?

Intermittent fasting is an eating pattern that some people use for weight management and general health. Some benefits have been reported or studied, though research is still developing and results vary from person to person:

• Support with weight management
• Possible effects on the renewal of cells and on hormone balance
• Possible effects on feelings of stress
• Research on the body's clearing and recycling of damaged cells during longer fasting periods
• Possible effects on blood sugar and insulin sensitivity
• Possible effects on triglycerides and cholesterol

Who Should Avoid Intermittent Fasting?

Although intermittent fasting is an eating pattern that some people choose, there are people who should not follow it. These are:

• People with a body mass index (BMI) below 20
• People with chronic conditions affecting the liver or kidneys, or conditions involving hypoglycaemia
• People with metabolic conditions
• Children under 18
• People with an eating disorder
• Pregnant and breastfeeding women

People with type 2 diabetes, low blood pressure or high uric acid should only follow intermittent fasting under their doctor's supervision. If you take regular medication, please check with your doctor before changing your meal pattern.

This article is for general information only; please consult your doctor and dietitian about your own situation.