Dr Caryn Zinn talks to us about fasting – why people fast; different types of fasting; and fasting experiences during the lockdown.

Why do people fast? Well, fasting goes right back to the Bible. People undertook fasting for spiritual or mental reasons. Fasting was seen to be cleansing, and there must have been some kind of physiological or metabolic advantage to this as well, because throughout the ages, fasting has continued as a practice. Even today, there are certain times of the year when people fast, such as Ramadan, or in the Jewish calendar, Yom Kippur, and the spiritual connection is maintained. From a physiological perspective, people are fasting more and more now. Reasons for people to fast include establishing, achieving and maintaining physiological benefits around either maintaining or losing weight; managing blood sugar; boosting the immune system to tap into autophagy and stem cell regeneration, and also improve inflammation. And people can use it for both prevention and management of cancer in cancer therapies. So, there’s a range of reasons why people fast.


Different types of fasting

Fasting can be divided into two main categories. The first one is intermittent fasting. It’s when you do a little bit every now and again, on a regular basis. Intermittent fasting can be classified into various different systems, for example:

  • 5:2, which was put on the map by Michael Mosley, and that refers to two days of the week where you restrict your calorie intake and you might miss a meal, such as breakfast. 
  • 16:8 – 16 hours of not eating, and eating within an eight hour window. This can also mean missing the breakfast meal. The reason why we talk about missing breakfast is because it tends to be the one that is easier to miss. We typically have dinner with our families, or in a more social circumstance, and it might interfere with family dynamics if you choose not to eat your dinner. But of course, some people who live alone might decide that not eating dinner would be a better way to do it, and eating a bigger, high-quality breakfast to account for all your nutrients.
  • OMD – one meal a day, or fasting for 24 hours. This can be particularly useful and still considered to be intermittent. It’s something you can do more frequently throughout weeks or months.
  • Alternate day fasting
  • Super-fasting – this one was coined by myself and my colleagues when we wrote the book What the Fast. This is when you do two lots of one meal a day fasting in a row. So, two lots of 24 hour days where you have your dinner meal only, and the rest of the time you eat low-carb, whole food, and then on the weekends you might take your foot off the brake a little bit and have a treat here and there. The beauty about super-fasting is for those people who want to get into a state of nutritional ketosis. For those of you who are keto all the time, you’ll know that it’s quite a challenge to keep up being in nutritional ketosis constantly. Super-fasting helps you establish that state and you can almost cycle in and out of ketosis and that can be very useful for people.


Advanced fasting

Here we are talking about anything from 48 hours and beyond. While intermittent fasting is something you would do to lose a bit of weight or see good outcomes in your blood sugar management, advanced fasting is looking for the outcomes in addition to those. It is more about tapping into the advanced metabolic benefits from fasting, which is stem cell regeneration; autophagy; giving your immune system a bit of an overhaul and a boost; and getting some quite profound keto, or anti-inflammatory, signalling going on in your body. It’s called advanced fasting for a reason. I would really recommend anyone who is going into advanced fasting to do their homework and read up a lot before-hand. Your electrolyte balance becomes incredibly important during this time, and you need to know what you are doing in order to get the benefits out of this.


Fasting during lockdown

Fasting can be your best friend or your worst enemy at any time of life, but particularly during lockdown, when our emotions and our stress levels are slightly (or enormously) heightened. Like everything in nutrition, there’s not just one system or one set of advice that works for everyone.


If fasting is just too much for your brain capacity or your stress levels right now, leave it for another time.


I’ve got some clients that just can’t face fasting during this time. Despite their weight loss goals, their blood sugar controls, they just need the comfort of eating. Because eating is a comfort. We need to make sure that we eat good quality foods. We still get comfort from eating good quality foods. If fasting is just too much for your brain capacity or your stress levels right now, leave it for another time. We’re not going to be in lockdown forever. There will be plenty of time to get into fasting. If you have weight-related goals, just aim for weight maintenance during this time, or work on the other things that can really affect weight loss. For example, use the extra time (if you’ve got the extra time, if you’re not an essential worker) to do some exercise, because exercise is not only something that makes you more insulin-sensitive and improves your immune system, it also boosts autophagy, and it also improves your sense of wellbeing. It helps secrete endorphins and it’s a calorie burner. So, exercise could be your friend if fasting is just not working for you at the moment.


Nutritional ketosis gives a lot of people a sense of calm.


I have some clients who are thriving on fasting. Some of them are doing super-fasting on Mondays and Tuesdays, and they are finding that having that one rule, not to eat at all, works well. If you do something like super-fasting or fasting for more than 18 to 24 hours, it might get you either closer to, or deeper into ketosis, and nutritional ketosis gives a lot of people a sense of calm. This might be from the fact that your blood sugar is more stable. It might be from the fact that the ketones are circulating and signalling, and establishing a sense of clearing brain fog. Getting into nutritional ketosis by fasting, for some people, ticks the boxes of creating rules and also helps them feel calmer.

Remember, fasting should feel good and it should enable you to achieve your realistic goals. As soon as something is a little bit off – if you’re not feeling good, if you feel like your energy levels are decreasing rather than increasing, and if you feel that you’re losing muscle mass – then it’s counter-intuitive and probably not worth your while.

I’d like to give you three scenarios where fasting can be used in a lockdown situation.

  1. If you have excess body fat, if you have prediabetes, type two diabetes, or high blood pressure, this might be a good time to try some intermittent fasting. You probably already know that the comorbidities that are strongly related to Covid-19 deaths are those three – type two diabetes, hypertension and obesity. So, this is the perfect time for you to really work on your health goals – putting your diabetes into remission by getting rid of some excess body fat, which will have a flow-on effect of dropping blood pressure if you’ve got hypertension.

If this is you, and you would like to try some fasting, start slow and go slow. You might start with missing two breakfasts a week and see how that goes. If you feel good, and if you like the rule, then you can extend that a little bit. It’s a matter of being in tune with your body and listening to your body.

  1. If you have been involved in a sport that is now on hold, or you have a health-related goal, you should try to maintain what you were doing to be in the best possible condition that you can be, because when we come out of this situation, life will resume in some shape or form, and you don’t want to go from ‘hero’, where you were before lockdown, to ‘zero’ when you get out of lockdown. That’s going to be very counterintuitive and counterproductive to your health goals, long-term. I would suggest using the one meal a day or the super-fasting strategy to get that body weight off. It can be incredibly powerful.
  2. The third type of scenario is if you are one of those ‘stressy’ types (if you are, you’re probably nodding and smiling right now). If your normal personality is now compounded by this uncertainty and stress of lockdown, your cortisol levels are probably sitting a little bit higher than normal. If you do too much fasting at this stage, your cortisol levels are going to shoot up even higher and that might cause some negative outcomes. If you still want to do some fasting, start low and go slow, maybe by missing a breakfast or two. Evaluate as you go and if it feels okay, if you tap into ketosis and that makes you feel a bit calmer, and if you’re happy with something that you can control with your food intake, then that’s absolutely fine. As long as it ticks the boxes of meeting your goals and you’re doing it in a safe and sustainable way, then there’s nothing wrong with it.

I will finish by offering you a challenge. Lockdown is a real challenge and it’s stressful, but it’s also an amazing opportunity. Let’s see if you can come out of lockdown fitter and healthier than before you went in!

Remember, this is going to be with us for a long time, so it’s really important to look after yourselves – look after your bodies and look after each other.