What is intermittent fasting?
Written by Daily Fix - Published 07-Aug-2022, last updated 25-Jul-2024
Intermittent fasting, or IF, is an eating pattern where you fast intermittently, restricting your "eating windows". There are many different variations of intermittent fasting including 16/8 fasting, which involves eating normally for 16 hours and fasting for 8 hours, and 5/2 fasting, which involves eating normally for 5 days a week and fasting for 2 days a week.
There's also "one meal a day", commonly known as OMAD, where you eat only one meal per day.
Advocates of intermittent fasting say that it can help you lose weight and improve your health.
This article is written by someone who started intermittent fasting about 12 months ago and has been following the eating regime ever since. It is not intended as medical advice and we strongly suggest you consult your GP or a diet professional before embarking on intermittent fasting.
What is the theory behind intermittent fasting?
Intermittent fasting breaks the cycle of "grazing" that is commonplace these days - eating little and often without giving the body a break.
When we eat the body breaks down carbohydrates quickly, and glucose travels directly through the walls of your intestines and into your blood. This results in rapidly increasing blood glucose levels, usually peaking at around 30 minutes after eating and returning to fasted levels after about 2 hours. So if you are snacking every few hours you can see how you body is experiencing spikes in blood glucose levels multiple times a day.
Intermittent fasting breaks this yo-yo of rising and falling blood glucose levels by prolonging the period when your body has burned through the calories consumed during your last meal and begins burning fat.
What are the benefits of intermittent fasting?
Intermittent fasting affects everyone differently, and the results you experience may be different from the effects it has on other people.
Speaking from experience, moving to intermittent fasting resulted in weight loss, a reduction in that mid-afternoon energy slump, better overall energy levels and fewer incidents of feeling bloated or having an upset stomach.
What are the different methods of intermittent fasting?
There are lots of different ways of intermittent fasting. Finding one that works for you is the key to forming a habit that you can stick to.
You may start on one method of intermittent fasting and then move to another as your body gets used to the change in your eating habits.
The 16/8 method of intermittent fasting
Spoiler alert - This is the pattern that works for me. In 16/8, your eating pattern is 16 hours of fasting and an 8 hour window during which you can eat.
16 hours fasting time may sound a long time, especially if you are used to eating breakfast as soon as you get up and eating throughout the day, culminating in dinner at 8 or 9pm.
Cutting out breakfast is one of the easiest ways to achieve an extended fasting period. Pushing back the first meal of the day to midday with the final meal just before 8pm achieves the 16 hours of fasting and 8 hour eating window. To start with you may struggle not to eat your bowl of cereal, slices of toast or full-english breakfast soon after waking up, but I found that soon after beginning intermittent fasting I had not hunger pangs or desire to eat as soon as I got up in the morning and I haven't eaten breakfast since embarking on intermittent fasting.
The 12/12 method
If 16 hours of non-eating sounds unachievable to you they you could start by fasting for 12 hours and having a 12 hour eating window. You probably sleep for 8 hours per night, so you only need to make sure you don't eat for 2 hours before you go to bed and 2 hours after you get up to achieve 12 hours of fasting. You can do that can't you?
One meal a day
Seen as the "ultimate" intermittent fasting pattern by many people, "one meal a day" (or OMAD for short) is exactly what it says - just one meal per day. When you choose to eat that meal is up to you, it's whatever works for you. Try skipping breakfast and having your first meal of the day sometime between midday and 2pm. This should then fuel you for the rest of the day so that you don't feel you "need" to eat again before you go to bed.
I tried one meal a day and it didn't work for me. Knowing I could only eat once per day was something I could not stick to long-term. I do, however, fit in a couple of one meal a day episodes per month, usually finding it's easy to achieve on busy days when I seem to be running about here, there and everywhere all day and not having the time to think about food!
Alternate day fasting
As the name suggests, this is when you fast every other day.
There are several variations of the alternate day fasting plan. For example, alternate day fasting can see a complete avoidance of solid foods on fasting days, while other people allow up to 25% of their usual calorie intake during fasting days.
On non-fasting (feeding) days, people often choose to eat as much as they want to fuel their body and get ready for the next fasting day, though don't overdo it!
A study publised on the National Library of Medicine reports that alternate day fasting is effective for weight loss and heart health in both healthy and overweight adults. The researchers found that the 32 participants lost an average of 5.2 kilograms (kg), or just over 11 pounds (lb), relative to the control group over a 12-week period.
The 5/2 eating pattern
The 5/2 eating pattern or 5:2 diet is slightly different to the intermittent fasting eating patterns described above, but it's very simple to explain. For 5 days per week, you eat normally and don't have to think about restricting calories. Then, on the other 5 days, you reduce your calorie intake to a quarter of your daily needs. With men usually needing around 2,500 calories per day and women 2,000 calories this works out to 600 to 750 calories for men and around 500 calories per day for women.
This eating pattern was made famous in the UK by Michael Mosley, a doctor and science journalist, following a feature in his BBC documentary, the 5:2 diet is based on intermittent fasting.
Drinking tea, coffee and water whilst intermittent fasting
One thing that I found helps me stick to my chosen intermittent fasting method was drinking plenty of black tea, black coffee and water. This does not interfere with intermittent fasting as black tea, black coffee and water have no calories.
Whenever I'm struggling to resist eating outside of my eating window I drink a large glass of water and a cup of black coffee. This does a great job of distracting me from my feelings of hunger and helps keep me going until my eating window.
Which pattern of intermittent fasting should you choose?
There's no correct answer! Choose the pattern that suits you, your lifestyle, your commitments and your family.
You may find that you want to use more than one pattern of intermittent fasting, and that's OK.
What is Autophagy?
Wikipedia defines autophagy as "the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent regulated mechanism". But what on earth does that mean!
In more simple terms, cancer.gov describes autophagy as "a process by which a cell breaks down and destroys old, damaged, or abnormal proteins and other substances". Think of it as the body starting to eat itself (auto: self, phage: eat), destroying and recycling its own damaged cell bits and proteins, so that new and healthy versions can be built.
When does autophagy start?
Estimates for the amount of time it takes for autophagy to start range from 18 hours to 4 days, with some experts saying that longer fasting periods results in increased benefits.
Are there any side-effects of intermittent fasting?
What you experience is likely to be very personal to you, but you may experience some headaches and constipation. You can limit the risk of this by making sure you are drinking plenty of fluids on your fasting days and eating plenty of vegetable and fruit. Drinking water keeps up your hydration levels, but it can also help suppress your appetite and, in turn, help you stick to your fasting commitments.
Don't jump headfirst into intermittent fasting, ease your body in slowly and increase the fasting period over time.
Conclusion - Should you try intermittent fasting?
Right at the start of this blog on intermittent fasting I wrote that nothing in this blog should be taken as medical advice. But from personal experience, intermittent fasting has resulted in weight loss, reduced body fat percentage, increased energy levels and less desire for unhealthy foods.
So if you like the sound of that, seek advice from your GP or a diet professional to see if you should give intermittent fasting a try.
FAQs
Yes, you can and should consume water and other non-caloric beverages (such as black tea and coffee) during fasting periods. Staying hydrated is essential for overall health and helps reduce hunger cravings.
Intermittent fasting may not be suitable for everyone, especially those with certain medical conditions or who are pregnant or breastfeeding. It's always recommended to consult with a healthcare professional before starting any new diet or lifestyle change.
Many people experience weight loss with intermittent fasting due to its potential to reduce calorie intake and promote fat burning. However, individual results may vary depending on factors such as diet, exercise, and metabolism.
Yes, you can continue exercising while following an intermittent fasting regime. In fact, many people find that exercising in a fasted state enhances their performance and accelerates fat loss. However, it is important to listen to your body and adjust your exercise routine as needed.
While intermittent fasting is generally safe for most people, some individuals may experience side effects such as hunger, fatigue, or irritability during the initial adjustment period. It's crucial to listen to your body, stay adequately nourished during eating periods, and stop if you feel unwell.
Yes, there are several popular methods of intermittent fasting, including the 16/8 method (fasting for 16 hours and having an 8-hour eating window), alternate-day fasting (eating normally on some days and drastically reducing calorie intake on others), and the 5:2 diet (consuming a normal amount of calories for five days and limiting intake on two non-consecutive days).
Intermittent fasting works by tapping into the body's natural ability to burn stored fat for energy when food is not readily available. By extending the period of time between meals, it allows the body to enter a state of ketosis, where fat becomes the primary source of fuel.
Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. It involves restricting your calorie intake for specific time windows, typically ranging from 16 hours to 24 hours.