I failed my fitness test 2 months before i went to the 'died in June/July 2005 because i was told to do it or get charged even though i had a light duties chit from the med centre due to an ankle ligament problem. I failed it and explained to the PTI's why. I also did my 2 months in the Gulf where i was given a glowing report for the effort and commitment i put in.
I'm overweight (and know i shouldn't be) but outperformed several skinny personnel who were out there at the same time as me. All i did was heed the advice about fluid intake and ate sensibly in the mess.
Fit for duty is different to fit by a required level. An RAF cross country runner at Leuchars many years ago failed his fitness test because he knackered his knees due to having to turn 180 degrees at the end of the gym. So ultra fit person fails fatty test but can still go out of area.
By the way I'm off to Seeb in a couple of months wether passed test or not. Not sloping my responsibilites.