This post about Intermittent Fasting is the first in a series of reviews of popular diets – I hope you get some value out of it! Feel free to suggest other diets that you’d like to see reviewed in this series.
In 2013, medical journalist Michael Mosley popularised the concept of intermittent fasting in his book “The Fast Diet”. The book, which quickly became a #1 New York Times best seller, followed on from his successful documentary “Eat, Fast and Live Longer” in which Michael set out to test the health benefits of this long-standing practice found in many cultures and traditions around the world. The results, at least for him, speak for themselves – he reversed many biochemical markers of ill-health, leaving him with improved life expectancy, a smaller waistline and generally feeling a lot better.
Intermittent fasting can be done in any number of different ways. Based on his research, Michael chose to use the “5:2” approach. This meant he would eat normally for 5 days of the week and significantly reduce his caloric intake for the other two. The basic tenets of his approach are as follows:
- eat normally for your age, gender & activity levels for 5 days of the week
- eat a reduced caloric intake for two days a week – aiming for 25% of your normal daily calories. In practical terms, this usually looks like two small meals per day on fasting day, totalling around 500-600 calories
- … and that’s pretty much it!
Additionally, it’s important to note that the non-fasting days are not an excuse to eat poorly. The whole approach embraces a more healthful, mindful approach to eating, and includes eating nutritious foods on the non-fasting days.
What are the other options?
The basic premise of intermittent fasting is to allow your body to go through a period of reduced caloric intake on a regular basis. This has been shown to have a number of beneficial physiological effects (see “Pros” below).
Alternatives to the 5:2 approach include:
- Fasting on a daily basis for 14-16 hours, and eating within an 8-10 hour window each day. For example – Break your fast at 11:00am, and don’t eat anything past 7pm. Using this method, you are effectively introducing an increased fasting window on a daily basis. This is a popular and simple approach, in which you don’t have to count calories or have specific days where you’re eating very low calories. This may suit you better if you have an irregular schedule that makes the “fast days” more difficult to manage, if you struggle with low blood sugar or generally don’t enjoy limiting your calories.
- Fasting every second (or third or fourth etc) day – this way you can tailor the pattern to suit you. This can make it difficult to schedule in future events like celebrations, dinners with friends etc as you have to work out which days you are fasting on, but allows you the flexibility to find a pattern that works for you.
- Fasting only once a week – useful where weight-loss is not the primary goal – as two “fast” (i.e. low calorie) days a week will usually result in fairly steady weight-loss, at least initially. This option will still offer the benefits of giving your body a low calorie window to increase healing, immune function, and overall wellbeing.
- Less frequent fasting – most people who do this will extend the fast period to a full 24 hours. This may work for people who want the benefits of intermittent fasting and prefer to go a full 24 hours without food less frequently, in preference to more regular calorie restriction or fasting.
Let’s have a look at the benefits you can expect from intermittent fasting:
- There is no requirement to exclude any specific foods. Nothing is off-limits, although this is not to be seen as an excuse to load up on non-nutritious foods in between fast days!
- Improved insulin and leptin sensitivity and improve satiety signalling. This makes it a great approach for people looking to achieve steady weight loss without the metabolic consequences and rebound weight gain of extreme weight-loss diets.
- You don’t find yourself in a constant state of deprivation, needing to draw on your willpower and battle with the effort of restricting your food intake every day. Anyone who’s ever dieted will know how draining this can feel.
- Many people report actually starting to enjoy and look forward to their fast days. They report feeling more alert, focussed, clear-headed, energised and motivated on these days
- it can be a great way to rethink your relationship with food. Intermittent fasting can show you just how much “non-hungry” eating we tend to engage in during the course of our day, and can offer you a way to become much more mindful about how you experience and respond to your body’s hunger signals.
- Contrary to what you might think, eating lightly on two days of the week does not make you more likely to binge on poor food choices on the other days. Most people who try this approach report feeling less inclined to eat heavy or high energy foods following a fast day, preferring instead fresher, lighter, more nutrient-dense foods. Many also report a gradual reduction in appetite.
- And from a health perspective, the following benefits have been seen:
- decreased inflammation
- increased immune resistance
- improved wound healing, blood fat profile and insulin sensitivity
- increased fat burning while maintaining lean muscle mass
- there’s also some evidence that it will extend life expectancy
- Intermittent fasting is definitely not something I would recommend for people with a history of disordered eating, as it does require you at least at first to focus on calories and portion sizes.
- If you have a high daily caffeine intake and/or live with chronic stress, have poor blood sugar control or regularly suffer from low blood sugar (accompanied by the classic “hangry” symptoms), I would recommend that you do some work with a health professional first. If you are able to stabilise your cortisol, insulin and blood sugar before attempting intermittent fasting you are much more likely to find it works well for you.
- It is definitely not appropriate for children, pregnant women and breastfeeding women.
- You may experience some unpleasant symptoms especially in the early days – for example, headache, irritability, nausea and difficultly sleeping. These are usually attributed to low blood sugar levels, and in many cases will pass after the first 2-3 weeks of intermittent fasting. As with anything, if you feel like it’s not working for you, stop and seek advice from a health professional.
- If you like to snack throughout the day, or feel better when you eat regularly, or have tried intermittent fasting and experienced adverse effects, then this approach is probably not for you!
As with any lifestyle change – experiment until you find what works for you. There’s no one way to eat healthily.
The Bottom Line
Intermittent fasting may be worth a try if you’re looking for a way to change your eating habits to promote better health and wellbeing, lose some weight along the way, and don’t want to engage in restrictive diets or expensive meal replacements. From a clinical perspective, this is one approach that I have seen consistently good results with in patients, colleagues and friends. Most people find they can easily achieve steady weight-loss and maintain their low calorie days without too much difficulty, with the added benefit of being able to continue eating with their families, enjoying social occasions, and not having to constantly think about food. Anecdotal reports of improved health outcomes including reduced inflammatory markers, reduced auto-immune markers, complete remission of long-term gastro-esophageal reflux, reduced joint inflammation and improved fertility and hormonal health are common amongst people who’ve adopted this approach.
As mentioned above, if you have any history of disordered eating, or are concerned about how this approach may affect your relationship with food and eating, please avoid engaging in any caloric restriction or controlled diet programs. Always seek appropriate medical advice from a health professional before embarking on any diet or lifestyle change.
So, what do you think? Is this something you’d try? Have you ever tried it? I’d love to hear your experiences with intermittent fasting, or your reservations if it doesn’t sound like something you’d ever try. As always, feel free to ask any questions you have, or message me via my Facebook page. Thanks for reading!