I suspect you have triggered an age/BMI combo which is why it's a problem now
and not before...
This is probably very close to the reason why. There's a little thing called a 'cardiac risk table' or similar that is used in more and more medical assessments in recent times. Once you get older, increased BMI etc it starts putting you into the higher end of a chance to have a 'cardiac event'. It also takes into account if you're a smoker and elevated levels of cholesterol so it would become harder and harder for either a medical officer or in your case a CASA official to sign their name to it accepting the risk
All the best