Confused on 24-hour vs 36-hour fast from published books

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Confused on 24-hour vs 36-hour fast from published books

This topic contains 4 replies, has 4 voices, and was last updated by  bigbooty 6 years, 6 months ago.

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  • I’m new to the FastDiet and finished reading The Fast Diet book published in 2013 in which Dr. Mosley recommends a 24-hour fast. I haven’t started the diet yet however, in the FAQ section of this website, it says that a fast day is 36-hours. Because of this contradiction on 24 vs 36 hours, I decided to read The Fast Life book published in 2015 to find out how many hours the fast should be. This updated book indicates that a fast is 36-hours however, Dr. Mosley does NOT explain why he has REVISED the fasting period from 24-hours as per The Fast Diet Book to 36-hours as per The Fast Life book.

    Can Dr. Mosley please weigh in on why the fasting period has been revised? Is a 24-hour fast not beneficial/valid; what were the metabolic findings between a 24 vs 36 hour fast?

    Hi Fast and welcome:

    I don’t believe Dr. M has ever answered a post on this site.

    The timeframe has always been 36 hours. The 24 hours was given as an alternative for those that could not make 36. The problem with 24 hours is that it really carries no calorie restriction with it and people that do it usually go away because they don’t lose much weight. This post discusses the issues:

    There has only been one study I am aware of that addressed short term periods of fasting (like 16:8). It found no material positive health benefits came from eating in that time frame unless also accompanied by material caloric restriction:

    Recent research does show significant health benefits from short term fasting – like 3-4 day water fasts:; .

    Bottom line – don’t worry about time between meals and focus on cutting your caloric intake. If you want additional health benefits not associated with weight loss, get into three plus day water fasting. Here are some more tips:

    Good Luck!

    Dr. Mosley has updated his diet since 2013. He now recommends a minimum 13 hour overnight fast ( if you stop eating at 8 pm on a Monday, wait until 9 a.m or later Tuesday to eat), and now allows 800 calorie fasting days for both sexes. According to his publisher he is updating The Fast Diet book, but we don’t know when it will be available. Since his Clever Guts Diet is very popular and the focus right now, I’ll bet we won’t see it until sometime in 2018. Good luck, whatever you do!

    P.s. google Dr. Mosley for updated 5:2. In March 2017, he gave a great interview with The Telegraph in the UK.

    I should add these simplified fasting guidelines make 5:2 a whole lot less confusing. Overnight fasting is simple and easy to do, since you’re sleeping a lot of the time!

    @fastNhungry. If you are overweight it is highly unlikely that you will get into ketosis after 36 hours let alone 24. When I first started I was lucky to get into ketosis after 48+ hours (I used to do two consecutive days for a total of 60 hours of water only fasting). I now get into ketosis after 24 hours. Your body gets better at fasting the longer you do it, Ive been at this for over 2 years now. I now fast once per week for the health aspects, I no longer want to lose weight.

    Don’t worry about the length of time, just find a pattern that is doable for you. It needs to be sustainable and something you can do for ever more.

    Good luck.

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