You tend to look older when you lose weight after a certain age, especially in the face because there is less fat stretching the skin and smoothing wrinkles. Skinny people (and I'm one) tend to look haggard and that is very aging.

But yep, it is quite noticable to me he is not aging like Politicians in high stress positions usually do, and even looks a little younger. But then he doesn't drink or smoke or do caffeine. He does do Diet Coke and burgers which ain't healthy but I suppose it is genetics in the end.