As Limpe have said many times.
The word fit has been greatly abused.
Noone is deemed fit simply by looking at their lifestyle, external body or even with normal vitals like BP etc. Or even if they can run marathons etc
A sickly patient today can show perfect vitals and die tomorrow.
The word fit is only applicable when you did a full body scan with contrasts, and all vitals and blood test in the normal range.
I doubt anyone will do all the above.
Hence in my dictionary, noone is fit to say they are fit in this world.