For me I would like to say, that I would never been able to eat up to my TDEE on my normal days. I have a medical condition, underactive thyroid, and even though I take medicine for that, my metabolism is still working in the lower range. And above that, I am 54, so my age has lowered my metabolism about 10-20%. In the beginning I tried to eat about 1745 cals. that's what my TDEE was at that moment. But I didn't loose but gained weight. I was talking to my doctor about it and she said, I had to go down in calories if I want to loose wight, even though I had my 500 cals. fasting days.
For me I had to work out my own way to loose weight and still following the 5:2 ( 4:3 actually

- until now) As long as I want to loose weight I can not eat what I want on my normal days. I still have to count calories, and I accept that

. So my strategy - which is working for ME ( even though some people say it is not good) I eat about 400 cals on fast days, about 1200 cals the other days (weekdays) and again a little bit more in weekends 1400 cals.
I think we all have to work out which is best for every one of us. for me 5:2 is not working in its simple form "Eat what you want on 5 days, and fast 2 days with 500 calories" - but still this WOL is very good and a healthy way for your body too.. you just have to adjust yourself so it suits you

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At least that is my opinion

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Pia