I'm writing this review 18 months after reading the book because after this time I can conclude that it's been life-changing. On the book itself, I'd say it was a fascinating and compelling read. Fung clearly explains quite complicated physiological mechanisms and provides evidence that I found very convincing (with one exception). 18 months on, the bits that have stuck are not the complicated issues but simply: 1 My body, and especially my liver, needs a regular rest from eating and from the constant blood insulin levels that frequent eating produces. 2 I'm probably stuck with whatever level of insulin resistance (and consequent stored fat) that developed through my adult life (I'm over 60) but I can help prevent further damage. 3 I shouldn't feel hungry when I fast intermittently (This was the life changer for me because I found it's true!). 4 Try to avoid discussing your intermittent diet regime with family and friends. They will simply go on and on with the usual uniformed diet rubbish that I used to believe myself.

This is a very interesting book, but I’m quite surprised that it has such rave reviews because the diet Dr Chung is recommending is not new or even a secret. Dr Chung says as much himself (on page 233 of the paperback version). Basically, his diet can be summarised as follows: 1) Avoid processed carbohydrates and sugar/sweeteners like the plague (this is the most important rule of all – if you do nothing else, do this one thing). 2) Eat plenty of fruit, vegetables, fish, fibre and whole grains (so wholemeal, not white, processed bread, pasta and rice). 3) Eat fat and protein – it’s fine, they won’t make you fat. 4) Choose unprocessed home cooked meals over processed microwave ready meals if you can (to avoid the added salt, sugar etc). 5) Feast (Eat) for 12 hours and Fast (Sleep) for 12 hours. Don’t eat outside of a 12-hour window per 24-hour cycle. Cut it down to 10 hours if you can. 6) Don’t snack – stick to three meals a day (within the 12-hour ‘eating’ window) so your insulin/blood sugar levels have a chance to recover. 7) Don’t worry about eating breakfast – if you’re not hungry first thing, skip it (if you do eat, don’t eat sugary cereals or pastries). 8) Fast a couple of times a week to lower/reset your insulin/blood sugar levels. 9) Get at least 7-9 hours’ sleep at the same time each night to avoid sleep deprivation raising your cortisol (stress) levels. 10) Vinegar (acetic acid) seems to help lower blood sugar/insulin levels (although this is a recent discovery, so there is no long term, only short term, data to support this). 11) Don’t worry about exercise – it only accounts for 5% of weight loss. 12) Don’t beat yourself up too much over your lack of self-control - 70% of the tendency to obesity is inherited – just try and make the most of the 30% you have control over. So it looks like it’s a combination of: -The Paleolithic Diet (whole grains, fish, fruit, vegetables etc) -The Atkins Diet (low carbs/high fat) - Michael Mosely’s 5:2 diet (‘Fasting Diet’) - Professor John Yudkin’s 1972 book ‘Pure, White and Deadly: How Sugar is Killing Us’ Versions of these have been around for a while, in some cases decades, and they keep being rediscovered every few years. (The Low Carb/High Fat diet was ‘invented’ by Dr Banting in 1862 and a version of the Paleolithic Diet dates back to John Harvey Kellogg in the 1890s). The Insulin-Resistance Theory What is new however – and why this book is so interesting - is Dr Chung’s ‘insulin resistance theory’ which is evidence-based using over a hundred years of reliable research and which he goes through and explains in great detail over six parts and 18 chapters. Every assertion he makes has a reference note and there are 32pp of medical references at the back. This adds some credibility to what he is saying. Dr Chung’s insight/argument is that obesity is a hormonal problem, not a calorific one, so cutting down on calories never works because it simply slows down your metabolism. Weight is controlled by the hormone insulin which promotes the absorption of glucose (blood sugar) from the blood into the body to use as energy that keeps us functioning. Most glucose gets used up straight away, but any excess is stored as fat. Obese people have far too much insulin sloshing around in their system all the time, which leads to insulin resistance where the amount of insulin in their bodies is set at a permanently high level like a faulty thermostat. They should therefore aim to keep their glucose/insulin levels low at all times with no high ‘spikes’. Carbohydrates and sugar (in its various forms) increase insulin more than most things that we consume, so cutting down on these two items has the biggest, most immediate, benefit. Most of the book is taken up with a detailed explanation of this and ‘The Solution’ part is only 19pp at the very end. I have to admit there were times when, as I was reading through, I was tempted just to skip to the ‘Solution’ bit and ask ‘So, what’s the big secret then?’, but persevering is worthwhile because his explanations back up his conclusions. Dr Chung isn’t a ‘diet doctor’ as such and his original interest in weight loss came from treating patients with kidney failure. He is a Canadian kidney specialist and he realised that many of his patients’ kidney failure had been caused by type 2 diabetes and that the diabetes had been caused, in turn, by obesity. This was what led him to look closely at all the research on dieting that had been carried out over the last century or so to try and work out what worked, what didn’t and why. He makes it all sound very reasonable, but of course changing how you eat and then sticking to it for most of the time is always the most difficult part!

Great book. A glossary would be a good addition for the big words (offering a conceptual understanding) , of which there are not too many. It's not really a "diet" , that word infers a lifetime if you look up the derivation of the word. A lot of common sense and offers hope to all those people who've been counting calories for decades, not knowing weight gain is actually hormonal. The fasting aspect is another weapon you can add to your arsenal in the fight against obesity. I did a one page precis which I'll paste here. Hopefully someone will find it helpful.