Thoughts on the Fast 800 Diet

Having picked up Michael Mosley’s Fast 800 book a couple of months back I finally got around to reading it at the end of June. I’ve been toying with trying intermittent fasting for a while now, so this was kind of research. The approach centres on fasting, basically reducing calorific consumption down to 800 calories a day, with some additional elements of time restricted eating, basically eating within a certain ‘window’ of time each day to promote ketosis.

The recommended plan is a period of rapid weight loss (the Fast 800) by consuming just 800 calories a day for between two weeks and two months, followed by a less restrictive regime of intermittent fasting, whereby you fast a few days per week, and eat normally but healthily on the other days (the 5:2 diet). However, it accepts that sticking to Fast 800 for several weeks may not be practical or even advisable for everyone, so there is a degree of flexibility. Slower, but less intense weight loss options that are recommended include just doing the 5:2 or adding additional fast days without going the full Fast 800.

I decided that the full Fast 800 was unlikely to work for me, the severity of the restriction would be difficult to maintain, particularly at weekends. But fasting a few days a week, and doing time restricted eating on non-fast days was probably manageable. So, for the past two weeks I’ve been fasting around 3 to 3 and a half days per week. Basically, I’ve been fasting on Monday, Tuesday and Thursday, keeping my calories down to around 800. On Friday’s I’ve been fasting up until the evening but not sticking to 800 calorie limit (although still consuming less than a normal day). On Saturday, Sunday and Wednesday I try to consume all meals within an eight-hour window, typically noon till 8pm, although I have drunk the odd beer after this time. I chose these days because I’m in the office Monday, Tuesday, Thursday, Friday which helps restrict potential for snacking or large meals, whereas Wednesdays and the weekend have more temptations. 

   

So far, it’s gone pretty well, during the early fast days I did feel tired in the afternoons, and occasionally light headed (‘keto flu’ apparently), but it has gotten easier. I do feel mildly hungry for most of the day, but not as bad as I thought I might. The results are also encouraging, before I started I was weighing (on my scales) between 116.2kg and 116.8kg, this morning I was down to 113.0kg. I suspect the rate of loss will taper off, but if I can get town to between 111kg and 112kg for my next consultant appointment on 30^th July I will be happy. After that I’ll consider moving to 5:2 plus time restricted healthy eating as a possible long-term pattern. It will also help that we’re going to attempt to change our diet as a whole family, so out with sweets and highly refined carbs and in with more complex carbs and fibre.