I disagree, You would already have lost your youth. No hot girls are going to go for a 55 year old ah peh unless you are a celebrity. You will also be prone to health problems marked by a sudden deterioration in fitness. Better to live a day as a tiger than a lifetime as a lamb. Live fast, die young, and leave a good-looking corpse.
Your problem is not age but your perception of yourself after what you consider to be a chronological milestone.
Fitness only deteriorates if you let it. There is this Asian concept that old age is some sort of disease. In NZ, there are plenty of 60 year old cyclists, marathon runners and triathletes who hold their own against the younger competition. Age does slow one down but it's a slow process not a sudden drop off at a certain point in ones life.
I'm fitter now than I was when I was 30 simply because I have a lot more time to indulge in healthy activities. At 30, I had to spend evenings in a smokey KTV lounge to entertain clients. I now spend the evenings working out in a smoke free environment. I've never felt better in my life.
As for the chicks all I can say is that if you're a man of means, the opposite sex will be attracted. You might not appeal to the 18 to 25 year old category but there are plenty of attractive women in their late 30s and early 40s who would find the maturity and stability of a middle aged man very enticing.