Intermittent fasting is an eating plan that switches between fasting and eating on a regular schedule. Research shows that intermittent fasting is a way to manage your weight and prevent — or even reverse — some forms of disease. But how do you do it? And is it safe?

NMTBP explores the different types of intermittent fasting and discusses any potential health benefits it might have

Is intermittent fasting a new thing?

Intermittent fasting (IF) is when you go for extended periods of time without eating. This is followed by a period of eating normally. Your ancestors would have eaten like this, not because of choice, but because of food availability. They would have only eaten when they could find food, either by hunting or foraging. Nowadays, you no longer have to hunt for your food. So, you’re unlikely to fast unless you choose to

Intermittent fasting is a way of mimicking more traditional eating patterns

What are the different types of intermittent fasting?

There are different forms of intermittent fasting, some of which are more extreme than others. The most common are:

5:2 diets

Here, you consume only 500 to 600 calories for two days each week. On the other days, you would eat a normal, healthy, and balanced diet with your usual calorie intake

16:8 plan

This involves eating during an eight-hour window and fasting for 16 hours. So, you could eat from 10 am to 6 pm and then drink water, milk, tea or coffee for the remaining time

Alternate day fasting

For this form of IF, you’d fast every other day, which can be very difficult to maintain over the longer term

24 hour fast

People following this diet would fast for an entire 24-hour period, perhaps monthly or weekly

Research shows that it can take two to four weeks before the body becomes accustomed to intermittent fasting. You might feel hungry or cranky while you’re getting used to the new routine. But research subjects who make it through the adjustment period tend to stick with the plan because they notice they feel better

How does intermittent fasting work?

The idea behind intermittent fasting is that it gives your body a break from digesting food. This can potentially lead you to have fewer calories than if you were eating more regularly. Also, eating less often can have positive effects on your blood sugar levels which can be useful if you have prediabetes or type two diabetes

Intermittent fasting may also trigger a process called autophagy. This is where your body works to remove damaged cells from your body. Your body does this when it doesn’t have to focus on digesting food. There is some evidence to show that autophagy can reduce your risk of cancer and other chronic diseases, but more evidence is needed

Other potential benefits of IF include:

• improved gut health
• better sleep
• reduced cardiovascular risk factors, including lower blood pressure
• lower inflammatory markers (linked to many chronic diseases)

Does intermittent fasting lead to weight loss?

It might do. In several short-term studies, people did lose weight when they tried intermittent fasting. This is because you would likely be having less calories overall. But for some people, intermittent fasting can lead to overeating. This is because when you go without eating for a while, your body makes more of the hunger hormone ghrelin. This can lead you to eat lots when you break your fast. So, eating healthily and being aware of how many calories you have is still important if you choose to try IF

Is intermittent fasting safe?

Research suggests that it can be safe for healthy adults. But there’s not enough evidence to show what would happen if you did this type of fasting for a long time. There are also some circumstances where IF would not be suitable.

• if you’re pregnant
• have type 1 diabetes
• have a history of disordered eating
• have anxiety or depression

So, it’s worth checking with your doctor if you have any health issues or concerns

What can I eat while intermittent fasting?

During the times when you’re not eating, water and zero-calorie beverages such as black coffee and tea are permitted

During your eating periods, “eating normally” does not mean going crazy. Research shows that you’re not likely to lose weight or get healthier if you pack your feeding times with high-calorie junk food, super-sized fried items and treats

But what some experts like about intermittent fasting is that it allows for a range of different foods to be eaten — and enjoyed. Sharing good, nutritious food with others and savoring the mealtime experience adds satisfaction and supports good health

Most nutrition experts regard the Mediterranean diet as a good blueprint of what to eat, whether you’re trying intermittent fasting or not. You can hardly go wrong when you pick leafy greens, healthy fats, lean protein and complex, unrefined carbohydrates such as whole grains

How to start intermittent fasting

If the idea of alternate days or 24-hour fasting doesn’t appeal, there are other options. For example, most people could manage to eat within an 8-hour window. This can stop all-day grazing. You can choose the time of your 8-hour window to suit your lifestyle. If you get up early, you could eat between 9 am and 5 pm. But if you prefer to eat later in the evening, you could start at 11 am and finish your meal by 7 pm

There’s also some evidence that sticking to an 8-hour eating window is better than eating late at night and then having an early breakfast. So, try experimenting with different timings to see what is realistic and achievable for you

What should I consider?

• Make sure that your diet is still healthy and balanced. So, focus on eating a wide range of vegetables, fruits, lean proteins, healthy fats, and wholegrains
• You should eat enough to give you the energy you need to carry out your daily tasks, including exercise. Some people find that IF patterns such as alternate day fasting can make them struggle to concentrate, so the 16:8 pattern could be easier to manage

Overall, you should eat a healthy diet by reducing your intake of added sugars, saturated fat, and highly processed foods. But if you do choose to try IF then make sure it’s suitable for you and prioritise a balanced diet when you do eat