There must be something else about the fasting diet because quite frankly I don't believe the weight loss I've experienced. I've now done three fasting days and I reckon the number of calories I have missed out on is 6,000 tops. I have around 500-600 calories on a fast day and maybe 2,500 calories on a non-fast day so let's call it a 2,000 calorie decrease on a fast day.
Based on this I'd have expected to lose around 2 lbs across the last 2 weeks, maybe with another pound because I've been keeping an eye on what I've been eating and drinking a lot less beer.
Instead I've lost 6lbs (182lbs to 176lbs) which indicates to me that despite my efforts to drink plenty of water, there's a significant dehydration effect which doesn't bode well for future weight loss and/or when/if I shift to 6:1 and I rehydrate.
The NHS is guarded on the effectiveness of the 5:2 diet and intermittent fasting in general. It's more through a lack of evidence rather than there being an abundance of evidence to the contrary:
http://www.nhs.uk/news/2013/01January/Pages/Does-the-5-2-intermittent-fasting-diet-work.aspx
That said, yesterday was more bearable. I was still hungry but dinner (a 350 calorie bean chilli) really kept the wolves at bay until morning and was very satisfying.