Regular readers of my blog will know that I am very scathing of fad diets – not least because us gluten-free folks often suffer at the hands of  people thinking GF is a fad, not medical necessity. But (and it’s getting to be quite a big ‘butt’, hence the article) I have been intrigued by the recent slew of press coverage of the 5:2 diet – a diet which seems to have some kind of scientific basis behind it. I was intrigued by the promise of being able to eat my fill on five days a week, and fancied the challenge of validating my willpower on the other two days – could someone who spends all day reading, writing and thinking about food survive on just 500 kcals a day without getting the rage? Would it have any health benefits?

The science

The principle behind the diet is that you eat normally for 5 days of the week, and ‘fast’ for the other two (non-sequential) days. Fasting constitutes eating just 500 calories (for a woman) over the course of the day. This could be from one large meal, or smaller snacks throughout the day.

Even the usually sensible Hugh Fearnley-Whittingstall is on the Fast Diet. Adherents are keen to point out that ‘this one is different’ as it has some ‘actual studies’ proving that intermittent fasting can not only help you lose weight and reduce your body fat percentage but longer term help you to live longer. A little digging on my first ‘hungry Monday’ exposes that there are actually very few in human studies, and certainly none looking at the long term effects of this kind of ‘intermittent fasting’ (IF) (although there is more on alternate day fasting (ADF)).

I coughed up and bought the book, and whilst I was persuaded by some of the early sections, I felt the second half made some major unqualified leaps from the studies to the diet plan. Little rationale is given for the 500kcal limit, no adjustments are recommended for your BMI/activity level. The permission to eat as you fancy within the 500kcal limit (including snacks) seemed to me to defeat the object of fasting at all – it’s just a different form of a standard calorie restriction diet.

The fast days

Well, to start with they were hard! But by week 3, I was living on 500kcal with plenty of energy, happily managing light exercise and barely noticing the hunger. It helps to plan what you will eat on the day, so you don’t get to the end of the day ravenous and realise you have and allowance left. I discovered ways to be creative with your calories – you get more vegetables for your calories than anything else, so vegetable curries, soups and raw veg snacks go very far. Filling up on low GI breakfasts like porridge went a long way. Busier days are also better – less time to notice any tummy rumbles.

The feast days

The book promises that you won’t over-compensate on your non-fast days, as your appetite stays healthy but reduces. This doesn’t match my experience at all. I woke the morning after each fast ravenous and craving carbohydrates, and stayed insatiably hungry for most of the day. The book promises that it’s the act of fasting that helps with health and weight-maintenance, and that you should eat normally and not deny yourself the odd treat on non-fast days. My simple brain took this as permission to eat all manner of baddies I would normally avoid – sugary granola, chocolate, pudding after dinner, wine on a week night.

Yes, I had a whale of a time – I normally watch what I eat carefully every day, and feel guilty about treats. It was liberating not to worry about it – however it definitely reduced the impact of the diet; and I can’t help think is dreadfully unhealthy in the long term – as I felt myself slipping into a binge/fast pattern.

The  results

The results from my little experiment were not what I was promised. I maintained, but didn’t loose any weight – I don’t believe there is any magic to fasting regarding weight loss if you eat as you wish on the non-fasting days. It’s still a question of calories in < calories out if you want to lose weight – you could achieve that over the week by restricting slightly every day, or a lot on some days and not others.

Of course I can’t testify to any other health benefits, but I have seen changes in my approach to eating. Some were good – I started to eat more slowly and savour food – paying attention to my breakfast rather than watching the news, checking email and scoffing at the same time. I also learned to keep hydrated, upping my intake of water and herbal tea – a thirst I was often satisfying with food. I have learned not to have the ‘where is my next meal’ panic of coeliac at the first sign of hunger, and roll with it until it really is time to eat. I loved the power I felt at being self-controlled enough to stick to my limits on fast days.

On the downside I felt it would be very easy for me to lapse into an unhealthy cycle of guilt-laden binging, and powerful virtuous fasting. You can see why this diet is not recommended for anyone with a history of eating disorders.