I first became aware of Intermittent Fasting or the 5:2 diet a few years ago when a few friends were enthusiastically describing the benefits of it. I tried it without doing any reading, and barely managed the first day because I was just too hungry. Inspired to try again by someone who is roughly my height & size and had lost 5kg fairly quickly, I gave it a go, and quickly worked out for myself the major new modification in Mosley’s plan - that 500 is too few calories for most people but 800 is much more manageable. Over a year I lost 12kg, taking me from a BMI of just over 25 to the weight I was in my early 20s, a happy UK size 12, which I had not enjoyed since the Atkins diet 15 years earlier.
Unfortunately, like all diets, when you stop them, weight returns, and a combination of events, including two frozen shoulders, led me to regain more than half my lost kg over a year, and lose the motivation to tolerate hunger. I am still doing a modified 5:2 but cheating much more often than I should. When I saw a copy of The Fast 800 Diet for request on NetGalley, this seemed a good opportunity to try again by doing it properly. I’m interested in the science behind it and reassured that Mosley is a qualified medical doctor, albeit non-practising since he has spent most of his career in journalism/broadcasting.
The Fast 800 is written in a clear engaging style with a mix of personal anecdotes and opinions, reviews of relevant research and suggestions on how to combat common pitfalls. The principal ideas from the 2012 original - The Fast Diet - have not changed, and he begins by explaining the theories around how fasting affects the body’s metabolism, in particular with regard to insulin and it’s effects on appetite and fat storage. Mosley’s own story includes the diagnosis of type 2 diabetes which kicked off his interest in the first place, and how his almost evangelical enthusiasm for the benefits of his discoveries was triggered by the remission of his diabetes. His gleeful confessions about his own chocolate addiction help make him more relatable than your typical preachy celebrity nutritionist. A second book, The 8-week Blood Sugar Diet, was aimed specifically at patients with diabetes.
In the intervening years, large population studies have been done which support his theories, and this is what led him to update the plan and publish the new book. The key change, as mentioned, is that the magic number is now 800 calories, which is both safer and more manageable for most people. The new principle is Time Restricted Eating, (TRE), which means limiting food in take to only part of the day - he proposes 16 hours initially - so not eating after 8pm and before 8am, then reducing that interval to 12 or even 10 hours, which is not as difficult as it sounds. He’s a big fan of the Mediterranean diet, which makes sense as there is good evidence that consuming mostly plants, protein (including meat, oily fish and pulses) and lashings of olive oil is the key to heart health and longevity.
The first chapter explains the reasons behind the modern obesity and secondary diabetes epidemics, and stresses that obesity is not the patient’s fault because the combination of genes and environment make it almost inevitable. Mosley has a way of revealing facts that seem completely obvious but that had never occurred to me before - for example that we think we’re addicted to sugar, but that no one tucks into a bowl of pure sugar; it’s actually the combination of carbohydrate and fat in a 2 to 1 ratio that makes our favourite foods so compelling.
Subsequent chapters focus on the medical benefits of fasting and TRE, and then of rapid initial weight loss - which counters the long-established theory that slow and steady is the way to go - because of the psychological boost that rapid and noticeable change brings. He then explains the Med Diet in detail, and goes on to extol the virtues of exercise in complementing his plan, and advice on the role of stress in poor eating and how to combat it. The remaining chapters deal with the practical aspects of how to begin, who should be excluded, and common Q&As and pitfalls, while the second half is all sample recipes and suggested meal plans. This part is where the average wannabe dieter’s interest may wane: no matter how delicious salmon, kale and leafy greens are, the list of foods to be avoided - realistically forever if you want to keep the weight off - is daunting. I can live without cakes and biscuits but avoiding rice and bread is miserably hard.
I read this as an ebook and so had the usual surprise when you get to 80% and discover the rest is all just references, so the book is shorter and therefore more readable than expected.
My main criticisms is that considering that the author is British, all units are imperial - presumably for the American market - I can’t think in lbs and have no idea what a quart is.
He also promotes meal-replacement shakes and refers to his website for brand suggestions - but in fact the site only promotes their own brand which seem quite expensive. I would rather be able to easily buy small quantities from a supermarket or service station when needed, to be able to try out flavours than order a months worth of shakes which might be revolting. One of the major difficulties of a diet like this is finding suitable foods on the go - since consuming large amounts of fruit is not recommended, nuts are really only a snack and most snack bars are full of sugar.
Overall I would recommend this book to anyone looking for a new way to lose weight - I do intend to start over once I get home from my current travels, as I have lots of lovely new clothes bought to celebrate my previous new shape that are now uncomfortably tight, and this has given me plenty of new ideas on how to do it properly - and the reassurance that when you get it right, those ravenous hunger pangs will settle quite quickly.
My thanks to NetGalley for the arc in exchange for an honest review. The Fast 800 Diet is published on 24th December - timely for all those New Year resolutions?