The FastDay Forum

I'm interested to know if there is any science behind the 5/600 calorie limits on fast days and what constitutes a 'fast'? I can't help but feel that those limits seem rather arbitrary.

Some fast days I have next to zero calories, and some I come closer to the 600 limit. But days that ate 600 calories don't 'feel' like a fast, if that makes any sense.

I think it is somewhat arbitrary, but I think it is an educated target number that works for most people. From what I've read, a fast is when you eat less than a quarter of your minimum daily base requirement. So for me, 450 is more on point, but I give myself the 50 calorie wiggle room.

It's not a true fast, it's an "intermittent calorie reduction" of 75% which has been clinically tested and (from memory) gave similar gain for less pain.

There hasn't been an extensive analysis of the possible matrix of calorie levels and fasting protocols and diet composition.

Rather than having to mess around counting calories, I have opted for zero calories (except for one glass of red wine) on my fasting days. It also seems to me that this will enhance the other benefits you get from fasting. Has anyone seen that this is a bad idea?

[carorees]

For a small group of people a slow down in thyroid function had been observed after fasting for as little as 24 hours. If you fall into this group, going 36 hours on water only might be less effective than the 500 cal version. Otherwise it should be fine.

I do a 24 hour fast followed by a <500 cal meal.

No. Drinking water only is a proper fast.

I've been water fasting twice a week for about 2 months now. I find it easier than eating 500 cals because I just get into the mindset that I won't eat on a fast day and so don't think about food. I occasionally have a coffee with milk and half a teaspoon of sugar, but I've been reading even that can 'break' the fast and interrupt the benefits. I've lost weight, feel great and any negative side effects stopped after about a month.

I'm hoping that I'll get increased health benefits this way. I think the 500/600 cal approach is just to make the diet sustainable. A lot of people on here marvel at me water fasting, but I think that if you're going to truly manage hunger and learn about it you have to face it properly - Ie not think about even a small meal all day. It's worked for me. I know I won't die/ faint etc if I don't eat all day and that hunger comes in waves instead of building up to be unbearable.

I don't intend to keep this up forever, but I think when I reach my target weight I'll keep up one proper water fast per week (36-40 hours) or once a fortnight if that maintains my weight.

I've been water fasting twice a week for about 2 months now. I find it easier than eating 500 cals because I just get into the mindset that I won't eat on a fast day and so don't think about food. . . .

I'm hoping that I'll get increased health benefits this way.

That's my thinking. I've been doing one no-cal fast a week (32 - 42 hours) for the last six months. While it's a struggle to keep from losing weight (I'm on the underweight side of the spectrum) and from freezing, I feel much better in every respect. I've also been doing 16:8 on the other days, and that has added to the sense of well being.

It's good to hear other people are water fasting as it does seem a bit extreme/ unusual, but it works for me. I originally thought I would move to normal 5:2 maintenance - normal as in M Mosley's 6:1 with one day of 500 cals a week. But I'm now thinking I might keep up a one day per week water fast when I reach my target weight. I'm pretty jealous of your struggle not to lose weight - it's not something I've ever faced!