This should fit the riddle:
People have mixed feelings about me
Some people embraces age (eg kids wanting to grow up) while some people resist.
If people take good care of themselves, I will go up
If people remain healthy and free from accidents, they will grow up, and since their age increases
I can change people's appearances, view of the world and understanding
With age comes change in appearances, perspective and wisdom
Some people may want to flaunt me, however, many try to hide me
Kids may want to flaunt their advanced age as compared to other children. Some people also feel that age is a sign of their superiority. While there are some who are afraid to show their age.
But no matter what you do, I will show
People try to defy me, but they won't succeed
Despite make-up/plastic surgery/botox/good maintenance, age will still show in the physical body.
And no matter what, I will not go down
Age cannot decrease. Probably an apt news to show here will be this