Anyone still has their toned slim body from their 20s?

I feel like everyone I know who used to be toned and slim now look bloated if not got fat outright. Even I gained 8 to 10 kgs and can't seem to lose it. I used to never go beyond 65kgs.

A doctor told me it's part of aging (JFC right?) but I refuse to believe it.

Is there anyone here who still has the same weight and body from their 20s? Or is it really a lost cause and I'd just have to accept it's part of aging?