Although it was more than 30 years ago, I still vividly remember my first day at the Royal Free Hospital Medical School in London. There were a hundred of us gathered in a lecture theatre to be greeted by the dean. He talked for a while about our future medical careers, but there were only two things he said that really stood out. The first was that, based on previous experience, four of us in that room would marry. He was spot on; I met my future wife that day.
The other thing he said was that while we would learn an enormous amount over the next five years, within 10 years of graduating a lot of what we had learnt would be out of date. This was disheartening, but the point he was making is that science is constantly changing and that keeping up with those changes represents a huge opportunity, as well as a challenge.
I mention this story because although I trained as a doctor, I have spent most of my working life as a BBC science journalist, constantly exploring new medical claims. Recently, I've become the subject of my own documentaries, a guinea pig happily trying out different, science-based, ways to achieve better health.
These approaches, though based on good scientific research, often challenge what is routinely believed.
Two years ago, I went to my doctor with a minor complaint and as part of the examination she suggested I have a routine blood test. When the results came back she told me that I was a type 2 diabetic, with a fasting glucose of around 7.2 millimoles/litre. She also told me that my cholesterol was way too high and suggested I should start on medication.
This was a nasty shock, as my father had passed away at the relatively early age of 74. When he died he was on a dozen different medicines and suffering from a range of diseases, including type 2 diabetes, heart failure, prostate cancer and what I suspect was early dementia.
When I had that medical examination I was slightly oveweight, being around 85kgs (187 lbs). I wasn't carrying a lot of fat but the fat I was carrying was abdominal fat, the sort that wraps itself around your internal organs. Having a waist that is more than half your height is a bad sign. My waist was 36 inches (I am 5' 11").
Rather than start on drugs I began researching alternative approaches and came across researchers studying something called intermittent fasting. I decided to make a documentary for the BBC science strand Horizon, with myself as the subject.
In the course of making the documentary, Eat, Fast, Live Longer, I tried different forms of intermittent fasting, ranging from doing five days of almost total calorie restriction to alternate day fasting, where you cut your calories every other day. None of them was easy. Eventually I settled on a pattern I could manage to stick to, which I called the 5:2 diet.
On a Monday and a Thursday, I ate a quarter of my normal calorie intake, going down from around 2400 to 600 calories a day.
On this diet I lost 9kgs (nearly 20lbs), four inches off my waist and my body fat went down from 28 per cent to 21 percent. My blood glucose and cholesterol levels went down to healthy levels. Soon I began to sleep better (I stopped snoring) and felt more energetic, particularly on my fasting days.
The Fast Diet
After the documentary went out on the BBC in August 2012 people began to stop me on the street and tell me they had tried my 5:2 approach and done really well on it. They also emailed details of their experiences.
I have had grateful messages of thanks from doctors, surgeons, parish priests, politicians and a Nobel prize-winner. I have read, via our website (thefastdiet.co.uk) and through other websites, thousands of success stories. These are a small sample:
"I heard the author on a radio show and he made so much sense I tried the diet. I have never stayed on a diet before. I lost 40 pounds in a few months. It is six months later and the weight is still gone."
"I've now lost about 19lbs in five weeks, my body fat is down from 37 per cent to 33 per cent and I can take my jeans off without undoing them and I'm happy to do so if anyone will watch!"