To fast, or not to fast. That is the question! So what are the different fasting styles, and should we all be giving it a go?
It seems like everyone (okay, not everyone) is fasting these days. Not for religious or spiritual reasons, like Ramadan or Lent, though. It’s for their health and, as always, miraculous benefits are being promised once you incorporate it into your routine.
Now, when I talk about fasting, I actually mean intermittent fasting (IF).
Warning: this post may be triggering for people who suffer with disordered eating.
It’s a diet/lifestyle concept that’s been around for a few years. I was first introduced when Horizon did a special with Dr Michael Mosley, who investigated and presented the idea of intermittent fasting to lose weight and improve his overall health.
And, for him, it worked. He was able to shift a fair few pounds and has even published a couple of books on the subject. I actually had a copy of his first book for a while.
How does fasting work?
The very simple idea is that by fasting and only consuming water to stay hydrated, you’ll burn through your standard carbohydrate based energy stores and start burning fat instead.1,2 Sounds pretty simple, doesn’t it?
What’s more, this ‘nutritional stress’ can jumpstart the body’s natural cellular repair processes, which can reduce the risk of heart disease.1,2
Alternate day fasting
With this style, you do one day of eating nothing (only water is allowed) and then another day of eating what you like! And repeat. This means that, if you stick to it, you’ll have a fasting period of around 36 hours each time.3
This is the method that Michael Mosley advocated in his horizon show. With this approach, you restrict yourself to 500–600 calories on a fast day (men get 100 calories more than women) and then eat a balanced diet on the other 5 days of the week.
This is a daily approach where you fast for 16 hours of the day, and eat within an 8 hour window. You can set the time frame to suit your needs, so could eat from 8am til 4pm or have it later in the day from 12 pm til 8pm.
Does it actually work?
I’ve been doing my research, and here’s what I’ve found:
- A lot of studies compare IF with the more traditional calorie deficit approach for weight loss2,4
- Results show that IF is equivalent to a low calorie diet when it comes to short term weight loss, BMI reduction and waist/hip circumference2,4
- When it comes to keeping up lean muscle mass, IF may be better than a calorie restricted diet5
- Most studies are still in animals, and human studies tend to be in small groups, so it’s harder to get reliable data1
- There needs to be a lot more research in humans, especially for factors like mental function while fasting, long term results and safety1,2,4
So, should we all be fasting?
Personally, I don’t think I would do alternate day fasting or even the 5:2 diet (sorry Dr Mosley). I’m also not sure that I’d try the 16:8 diet either, but there is another option. The 12:12 fast. You eat in a 12 hour window, and fast for the other 12 hours. That means you can have breakfast at 8am, and finish dinner by 8pm.
This sounds most appealing to me as it gives a bit more flexibility. After all, plans do change! I haven’t seen much published research on this approach, but that hasn’t stopped other health and wellness websites from advocating it. In theory, 12 hours is a good amount of time for the body to start burning fat, and for natural repair processes to kick in.
I think, at the end of the day, that you need to consider certain factors before you try intermittent fasting.
First, you may not have that much weight to lose anyway (a lot of studies are done in overweight/obese people).
Second, your lifestyle may interrupt the best intentions. If this is the case, don’t punish yourself.
Third, the people who I hear the virtues of IF from are health, wellness or fitness influencers who have the time and the money to make IF work for them. Also, IF may in fact be part of their career, so they’ll definitely be putting a lot of effort in!
Finally, IF probably won’t cause a body transformation by itself, you’ll need to get moving too! After all, healthy living is not just a diet.
P.S. If you’re set on trying IF, please see a doctor or registered dietician first, and be aware that this practice can be a trigger for people who struggle with disordered eating.
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- Horne BD et al. Am J Clin Nutr. 2015;102:464–70.
- Harris L et al. JBI Database System Rev Implement Rep. 2018;16(2):507–47.
- Tripolt NJ et al. Adv Ther. 2018;35:1265–83.
- Seimon RV et al. Mol Cell Endocrinol. 2015;15(418):153–72.
- Varady KA. Obesity Reviews. 2011;12:e593–e601.
I did the 5:2 IF but sooner realised it isn’t for me, I felt groggy and cranky. After this post, I’m considering the 12:12, maybe because of the longer window time, I can eat my full.
Thanks for this post, great research!
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I’ve seen so many positive feedbacks from people who have actually tried IF. It’s intriguing. I had heard of 5:2 and the 16:8 method, but didn’t know that a 12:12 method is also there. That definitely seems more doable. I’m definitely interested in trying it out. Maybe for a week and then see how it goes.
Cool post. I hadn’t heard of a few of those and I like to think I normally know all the trends! Very interesting and thanks for the disclaimer about disordered eating. So important!