Intermittent Fasting

MARCH 2013 UPDATE: Since writing this article, a fantastic documentary on Intermittent Fasting has been aired on BBC. I’m glad this approach has had some mainstream recognition and I would say the program is required viewing for anyone considering giving intermittent fasting a go. Unfortunately it’s been taken off YouTube now, but you may be able to find it elsewhere on the web.

The idea of fasting has a bit of a bad reputation, and due to mis-information from food companies and the media it’s commonly thought that not eating for anything more than a few hours is dangerous and counter productive, as it causes your metabolism to ‘crash’.

Through my own experiences and research, I believe this idea of constantly eating frequent meals to keep ‘stoking the metabolic fire’ is misguided, counter-productive and just plain wrong. Sadly, it’s probably the most repeated and preached principle of nutrition.

The more skeptical side of me thinks it could be an incredibly successful marketing ploy by the food industry to get people to eat more meals, but then again I also think the moon landing was faked and the CIA killed John F Kennedy ; )

There are many great sites and resources written by people who’ve looked deeply into the subject of fasting. Therefore, I am keeping this post pretty short and to-the-point, with a lot of references to more in-depth information if you want to know more.

What is intermittent fasting?

Simply put, the act of fasting is the willful abstinence of drink and/or food for a pre-determined length of time. When looking at the Intermittent Fasting (shortened to IF) approach, it is abstinence from the consumption of calories for a set period of time, say, 18 or 24 hours. Zero or virtually zero beverages such as water, black coffee, herbal tea, sugar-free gum and zero-calorie soft drinks can be consumed.

Zero calorie drinks and sugar free gum are fine during fasts

Isn’t this dangerous?

For healthy individuals without specific dietary needs or requirements, no it’s not. It has long been established through research that eating less leads to a longer, healthier life. Constant calorie restriction is often difficult so for most people a far more practical and realistic approach is to periodically take controlled breaks from eating. Looking at it purely from a weight loss point of view, this approach helps to create a calorie deficit (more energy burnt than consumed) and improves the conditions for weight loss, such as a reduction in insulin levels. But it doesn’t stop there – there are also many other documented health benefits that are not just related to weight loss, such as:

  • Decreased body fat percentage
  • Reduction in blood glucose levels
  • Reduction in insulin levels and increased insulin sensitivity
  • Increased lipolysis (fat burning potential)
  • Increased levels of norepinephrine and epinephrine
  • Increased Glucagon and growth hormone (GH) levels
  • Decreased chronic inflammation

Quite a list, I’m sure you’ll agree. And all these claims are backed up by solid scientific research, unlike that so often repeated claim that eating every few hours speeds up your metabolism, which is not backed up by any credible evidence.

The fed and fasted state

The human body is always in one of two states: the fed state (post-prandial) or fasted state (post-absorptive). The fed state is when you are in the process of eating and storing calories from food or drink consumed and lasts about 2-6 hours after consumption. The fasted state is when you are in the process of burning the calories that have already been stored by your body in the form of glycogen or fat.

For a healthy body you need to strike the right balance between these two states – storing calories and burning calories. The trouble is, we are spending more and more time in the fed state, with some people spending 80-90% of the time processing and storing food. You don’t have to be a scientist to see that spending so much time in the state of consuming and storing is going to put a great deal of strain on your bodily functions and result in weight gain and other health issues.

Balance of fed and fasted states

Understanding and exercising balance is key to success in diet and life

The principle of balance is key to success in diet, nutrition and life. IF allows us to readdress this balance and is a sustainable and realistic approach to eating and weight/body composition management. By having periods of not eating (as opposed to constantly eating as many do now) your digestive system gets a break from constantly working and your pancreas gets a break from secreting insulin, resulting in a drop in insulin levels from the constant semi-elevated level that eating frequently causes.

In summary, whatever dietary approach you choose to take, gaining a healthy balance between the fed and fasted state is the key to success and results.

Approaches to Intermittent Fasting

I would say any dietary plan that involves taking controlled breaks from eating and keeps your body in the right balance between fed/storing and fasted/burning states can be considered intermittent fasting. However, it would probably help to get some structure to your plan and here are two approaches that I think are most effective and are backed by science, research and experience. There are other IF plans and sites out there, but If you’re considering trying IF then fully familiarize with the work of these two guys first.


Eat Stop Eat by Brad Pilon is probably the foremost guide to intermittent fasting written. This was the first guide I read on the subject and after reading it cover to cover I was sold. This book is full of references to studies and research that support Pilon’s claims. Whether you decide that IF is for you or not I would recommend reading this book as there are many interesting and thought-provoking ideas about diet, nutrition and the food industry.

In summary, Pilon advocates one or two 24-hour fasts from food and calorie containing beverages each week. This is not a whole day, but is, for example, 4pm one day to 4pm the next, or midday to midday. So you never go a full day without eating. His approach advocates eating pretty freely the rest of the week and is a flexible and realistic approach.

There is a good 20 minute video presentation on his site which gives you enough info to get started, but if you want a more in-depth look at fasting and the science behind it go ahead and buy his book (which comes with a money back guarantee).

Brad Pilon also blogs here.


Leangains has been around for years and takes the approach of a 16 hour fast each day, so you consume your food during an 8 hour feeding window of, say, midday to 8pm. Some may say that the author Martin Berkhan is a little too lean judging by the photos, but it can’t be denied he’s got astounding fat loss and muscle gaining results for himself and clients.

Martin is a little stricter than Eat Stop Eat with his recommendations for what you consume, advocating clean, whole healthy foods (with occasional treats, of course). He also looks at tying your training in with your fasting when GH and other hormone levels are at their optimum levels, giving the best fat-burning and muscle building results.

The Leangains approach is not as flexible as Eat Stop Eat, but it’s tried, tested and effective. Read through the articles on his site for some interesting insight.

Resistance training

The above two sources look closely at the science and application of intermittent fasting so I haven’t delved too deeply here into that side of things. However, there is one point that I think is so important that I will touch on it here, and that’s the need to accompany IF with some form of resistance/weight training. This element of a successful approach to IF is ‘non-negotiable’ as it will help to preserve, maintain and build lean muscle mass, which gives that often desired ‘ripped’ or ‘toned’ physique. So in other words, the diet has to be complimented with the exercise.

Coupling intermittent fasting with some form of resistance training is crucial for success


Intermittent Fasting is suitable for healthy individuals and those over 18 years of age. You should consult a doctor, dietitian or physician before embarking on any diet, eating plan or exercise program.

Final word

I believe that this approach is the most effective way to get in shape and lose body fat whilst maintaining muscle. I also believe that it comes with many other health benefits. When we consider how we’ve fueled our bodies as they’ve evolved there would have been periods of eating (when we’ve hunted and caught food) and periods when food was more scarce and we weren’t eating. The constant eating and excess consumption that many of us practice now goes against this, and is contributing to obesity, diabetes and other related diseases.

And the best thing about it? The flexibility offered by the approach means that I can honestly say that I’m in it for life. How many people can say that about a strict diet plan or calorie counting?

Further reading

This was a brief introduction to intermittent fasting. If this has sparked your interest then go out there and do some further research to see if it’s for you. Start here (in rough order of importance):

Eat Stop Eat by Brad Pilon

Leangains by Martin Berkhan. Here is a brief outline of his approach.

The Sam Effect has a great overview of Intermittent Fasting

The IF Life offers more insight into IF.and ‘2 Meal Mike’s” approach

Here is Wikipedia’s page on Intermittent Fasting

Natural News reports on a study indicating that IF promotes brain health, another benefit reaching beyond simply weight loss.

Mark Daily Apple’s musings on IF

That should be enough to get you started. Let me know how you get on with this and if it works for you…. Good luck!

6 thoughts on “Intermittent Fasting

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