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5:2 Diet 'Rules' & Variations

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It's Thursday so I'm fasting, going into my third week with this. I'm a bit hungry but I really don't feel like eating.

Am i "allowed" or "supposed" to eat my 600 kcal?

It's evening now and I've only had about 100 kcal, and I don't really think I want to eat 500 kcal more, maybe 100-200 instead. I don't know yet.

Is eating less than your dose of calories counterproductive in some way, for weight loss or health purposes?
It's a rule of thumb generalized for a large population.

Allowed is the answer. You can eat less - or up to 1/4 of your calculated TDEE - but not generally more.

I find that I always eat less than my TDEE on feast days and right at 600 calories on fast days.

I eat a single fast-day meal in the evening rather than dividing it across the day. I appreciate it more and there's evidence in the book that nibbling them away during the day reduces weight loss.


You can eat 600 or less. Many people start at their 'allowance' and work down - sometimes to 'liquid fasting' or 0 cal. on fast days. They usually do this in an attempt to lose weight a little faster, but some just like not eating for a day. As you probably know, 5:2 was not designed as a weight loss diet, and the 600/500 number was picked as a minimum number that produced the desired changes in body function and blood work for life extension purposes (hopes). :neutral:
I quite often will only have a cuppa soup for my fast, 50-100cals. Today however I feel like I really want something solid so will have a giant salad for around 200-250 cals, and that'll be all :D
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