I was always told it was a bit of trial and error and to always pick sedentary as fitbits etc over estimate exercise. However if you're eating at 1700 and losing weight then go for it. It might slow down a bit after a while and then you can readjust.
I never eat back my calories from exercise personally as I just don't trust it's tracked that accurately however it does give me a little bit of leeway if I've gone over on a different day.
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I'm so happy to be back at the gym, I do their workout of the day and it was skipping and weights yesterday and my tummy muscles are so sore don't even know why!
Cardio tonight, I'm trying to get back into couch to 5k. I was all the way up to week 5 before lockdown so I started week one recently and it was a bit too easy so going to maybe try midway through week 2 tonight.