Think Fast: The 5:2 Diet Book Review

If you have been reading this blog for long, than you know I abhor quick fix weight-loss schemes and have no time for detoxes, cleanses, or extreme diets.  There is no evidence to support the efficacy of detoxes or cleanses and most people cannot sustain a really restrictive or low calorie diet long-term.  The goal for anyone should be to establish healthy habits that can be maintained over the lifetime. 

So initially when I started to hear about intermittent fasting, I rolled my eyes and sighed.  "What now," I wondered, "A diet where you just don't eat at all?"

But intermittent fasting is actually a weight loss or maintenance technique that is backed by science and supported by weight-loss experts I respect like Yoni Freedhoff.  So when I was asked to review Kate Harrison's The 5:2 Diet Book, I enthusiastically agreed.

There are many variations that one can take on this eating pattern: short cycles of complete fasting (1-2 days a week consuming nothing), a few days a week of restricted intake with normal eating on other days, or even limiting eating to specific hours every day (eating between 10am and 7pm, and then not eating again until 10am the next day). 

Regardless of what physiological benefits may underlie brief periods of fasting, what makes this approach so effective for many people is the psychological benefits of only having to restrict their eating for short periods of time and being allowed to resume regular eating patterns the rest of the time.

Harrison is not a physician or dietician, but a journalist who has become an advocate for this weight loss strategy.  It helped her shed significant weight through a cycle of consuming just 500 calories 2 days a week, and a 'normal' diet of about 1,800-2,000 calories on the other days and maintain the loss for a number of years.

The book is surprisingly entertaining.  Who knew a book about dieting could be enjoyable to read?  Given that Harrison is a journalist, I guess it should be no surprise that she writes well, and in an appealing way for lay folks.  If you like to know basic information about things but don't like reading a lot of detailed science info, than you will like this book.  That being said, if you do like to know the how and why of things, she lists a lot of resources at the end.  It is mostly a description of how she adapted to this eating plan as well as many anecdotal stories from others who use intermittent fasting to lose and maintain their weight.

One thing she mentions at the beginning which is very important is, do not attempt this type of eating plan without first consulting a doctor.  It is not suitable for anyone who is pregnant or breast feeding, or who has a history of an eating disorder.   If you are prone to clinically significant binge eating, this eating pattern is probably not for you.  If you have any type of chronic illness, such as diabetes, it really is critical that you speak to a health professional first.

What's great about this diet is you can eat whatever you want: vegan, omnivorous, low carb, gluten, gluten-free, paleo, the traditional foods of your culture, etc.  Eliminating entire food groups is not necessary.

I think, given most North American's reticence to making major changes to WHAT they eat, changing HOW they eat in this way may be a good solution for some people.  The periods of restriction are short, which makes them more psychologically manageable.

Now, to be honest, I have my doubts that I could pull off eating just 500 calories in a day.  But I am extremely physically active, and have always had a very large appetite.  But Harrison does say that as she got used to this system, she became able to workout, even on fast days.  She even says that she actually enjoys her fast days as she has a sort of set routine, and therefore doesn't have to think about what to eat, and they make her feel 'cleansed.'

What I object to is what she recommends eating on fast days.  There is some theory about protein interfering with the physiological processes underlying the health benefits of fast periods.  But - and she does admit this herself - protein helps you feel full.

Actually, if you would like to attempt intermittent fasting, I would refer to Barbara J. Rolls' book Volumetrics, which outlines what foods to eat to allow you to feel full on fewer calories.  It should come as no surprise that lower sugar fruits, veggies, lean proteins and high fibre foods are tops.  Understanding glycemic index is also important.  Ultimately, you want to fuel yourself with nutritious low-calorie foods that will keep you blood sugar as stable as possible.  Harrison does mention this too, however, some of the foods she mentions having as staples on her fast days are not necessarily ones I would recommend, like canned soups.

I also don't love the meal/food suggestions she gives at the end (packaged, sweetened oatmeal and white flour products would not be what I would recommend!), but that's what is so great about this: you can adapt it to suit your needs and preferences, as long as you stay within the calorie limits, which is 500 calories on fast days for women, and 600 for men, and then 1,800-2,000 calories on the other days.  She does, however, give suggestions for what to eat if you are out at a restaurant, etc., which, of course, can make things challenging. 

One key thing to remember is that 'other' days are not 'binge' days.  The key, like with any diet, is creating an overall calorie deficit, and you can easily negate the deficit on fast days if you go overboard on the other days.



I was also sent the accompanying recipe book by Laura Herring (sounds fishy to me, he he!).  I wasn't thrilled by this book.  Unless you really don't know how to cook and/or have no idea about how to track the calories of your meals, I don't think this is a must have.  Again, if you are limiting calories, there is no place for refined carbohydrates and there was white flour and sugar in these recipes, which I felt was really unnecessary.

In any case, if you have struggled to lose weight and are looking for something new to try and this sounds appealing to you, than see your doctor and/or a registered dietician and explore whether intermittent fasting may be for you.