A guide to Intermittent Fasting (IF)
The health benefits of Intermittent Fasting are starting to be recognised by progressive doctors and nutritionists around the world. But there is still a lot of discussion and confusion around how to fast. So what is the best way to fast? Well it really depends on your goals and what you want to achieve from fasting. If you have any underlying medical conditions, it is best to consult your doctor before undertaking any big change in diet including fasting.
Intermittent Fasting can be broken up into 2 groups. Clean fasts where you only drink water and non-caloric, non-sweetened drinks like black tea or coffee. Or Calorie Restricted fasts where you eat a small proportion of your usual calories during your fasting window, usually 25% or about 500 calories.
I prefer clean fasts for a few reasons, some of them biological and some of them psychological. More on that later.
Most Popular Types of Fasts
5/2 (or 4/3) Fast Diet
Popularised by Dr Michael Moseley of BBC TV fame, this fasting protocol has you fast for two days a week and eat normally the other days. During your fast days, you can eat up to 500 calories (600 for men). Other than that, there are no hard and fast rules on what to eat during your fast or normal days, just an encouragement to avoid sugar and use alcohol in moderation. He also suggests try to make your fast 36 hours rather than 24. So if you fast Monday and Thursdays for example, for your Monday fast, you would start fasting after dinner Sunday night and then your next meal would be breakfast Tuesday morning which should be close to 36 hours all up.
For those that want to speed up weight loss, Dr Moseley recommends the 4/3 method: That is essentially the same but 4 days eating normally and 3 days fasting.
Pros as I see it - The 5/2 is easy to follow, you can switch around your days to suit your lifestyle. Small amounts of food are allowed which is probably good for a novice faster worried about no food
Cons as I see it - Two days for some people is not enough for them to lose weight quickly so they give up. For me, 5/2 it a good maintenance diet, particular if I’m indulging on the weekends or overeating on non-fast days, but not great for weight loss (4/3 is definitely better). Anecdotally 5/2 seems to work well for men or people with a lot of weight to lose. I also don’t think you get the full fasting benefits (in terms of insulin regulation and blood sugar management) if you eat 500 calories. The key to get into fat burning as fast as possible is to use up all your blood sugar and stored glycogen and if you eat even a little, that process will slow down. And lastly, eating a little bit just makes me want to eat more. Thinking about and counting calories is time consuming and reinforces a ‘diet mindset’ rather than a lifestyle choice. In my experience, that diet mindset can often lead to overeating on non-fast days to compensate, thus undoing the good day's work.
Alternate Day Fasting (ADF)
Just as it sounds, this diet means you fast one day and eat normally the next. The most popular version of this is The Every Other Day Diet, based on the excellent research done by Dr Krista Varady, a professor at the University of Illinois. It is similar to the 5/2 Fast Diet in that you can eat 500 calories on a fast day and then whatever you like on what she calls ‘feast’ days. As you must stick to every other day, one week you fast 3 days, the next week it will be 4 days of fasting. Another popular version of ADF is the JUDD Diet (Up Day Down Day).
The pros and cons of ADF are very similar to the 5/2 Fast Diet except because you are fasting more, you will likely lose weight on an ADF diet (as long as you don’t binge on your feast days!) I still think eating a calorie restricted diet on fast days, while perhaps slightly more user friendly, will likely slow down results and for some, make it harder to stick to. For me, eating absolutely nothing is just much easier (and makes me less hungry) than eating a paltry amount. Also it means your fasting will always fall on a weekend, maybe OK for some but for those of us with active social lives, that can be problematic.
My recommendation for following both the 5/2 Fast Diet and an Alternate Day Diet would be to do a clean fast (that includes, water, sparkling water, black tea and coffee). Do not use any sweeteners, artificial or natural sugar in your drinks as research shows it will spike your insulin, which is slows down the body getting into ketosis (using your fat for energy).
This is where you clean fast for most of your 24 hours and pick a ‘window’ of time where you eat. The most popular form of this diet is the Fast-5 Diet created by Dr Burt Herring. The theory here is that you kick your body into fat burning mode every day but you also get to eat every day so its much easier to follow than a whole day of fasting. In the case of the Fast 5 Diet, you fast for 19 hours a day and you can eat in a 5-hour window. Most people skip breakfast and eat a late lunch or snack and then dinner but the plan can be flexible on when your window is. Incidentally, Dr Herring has written an excellent book on Appetite Correction, (which is a welcome and significant appetite change that happens when people follow a regular fasting protocol). Appetite Correction brings the hunger and satiety hormones back into balance so your body can return to its natural rhythm of eating (before we ate often nutritionally deficient food multiple times a day). Once Appetite Correction kicks in, you will be able to listen to your body’s natural hunger signals and rhythms (and hopefully say goodbye to habitual and mindless eating forever).
The minimum amount of time to fast to see any benefit would be 16 hours, which translates to a 16-hour fast/8 hour eating window. This allows most people to have at least 2 meals a day. While likely metabolically beneficial on some level, for people wanting to lose weight or make significant improvements in their blood markers, this eating window is just too long. 20/4 or even 23/1 will maximise fat burning time and limit the opportunity (time!) to overindulge when the eating window is open.
One Meal A Day (OMAD)
One meal a day is just how it sounds. You choose a meal a day (and it can vary from lunch one day to dinner the next) and eat only that. Other than that you clean fast. Nothing is off limits when you eat, the idea is to only eat once though so your fasting time is maximised. Again the simplicity of this is works well but weight loss may be slow and how realistic this is as a long-term lifestyle for some people is a real issue. A great book explaining OMAD and IF (written by a lay-person rather than a doctor or scientist) is Gin Stephens’ book, Delay Don’t Deny.
Extended fasts means fasting for more than 48 hours at a time (the world record for a severely obese patient was 382 days). Extended fasting is best done under supervision of a doctor or at a fasting clinic. There is research to say that many health benefits including autophagy, cell regeneration and anti-inflammatory markers kick in at the 72-hour mark. Many people use an extended fast to kick start weight loss too if they have been doing a fasting protocol for a while but their weight loss has stalled. Dr Jason Fung, a leading authority on using fasting to treat Type 2 Diabetes and author of The Obesity Code, uses (highly monitored) extended fasting with great success with obese type 2 diabetic patients. Most of us have enough fat to power us for a long time (we just need to get better at using it).
Ultimately the length and kind of fasting you choose is up to individual choice. The best thing to do is to pick one and get started and then you can always adjust or change your fasting regime as you get used to it. Remember, if you have any medical conditions, consult your doctor before beginning any fasting regime.
Fasting is not suitable for children, pregnant or lactating women, the elderly, people with underlying medical conditions or people who suffer or have suffered from an eating disorder in the past.