I don't think metabolism is an excuse, its actually more of a motivator if anything to be more health conscious as you get older. Hence me not wanting to eat 3k calories per day and a lot of junk at my age, compared to say when I was 25 years old where you don't care as much.
I mean, having to be more conscious of what you eat when you get older is not a crazy viewpoint, I think it is pretty common. You're in great shape, but I bet you have to work harder to stay in that great shape compared to someone who is 25, no? Or when you were 25. I mean look at your older pro athletes and the diet regiments they have to keep up with guys who are in their 20s. Chara, Chelios, etc.
I think the most disheartening thing ever was when me and friends went on a cruise when we were all 30, and I gained 12 pounds in one week from it. I didnt even eat anything too crazy although overall not super healthy, I just didnt exercise.