I started working out around my late teens. I lost a lot of weight and also left the worst part of puberty behind. I vividly remember how different everyone started treating me - Teachers gave me better grades, acquaintances were easier to turn into friends, ticket controllers on the train were more often understanding when I had forgotten to stamp my ticket, it was easier to interview for jobs, it was easier to get dates, it was easier to get into 21+ nightclubs, it was easier to get shit for free and friends and family started listening to me and taking me more seriously.
This wasn't a result of me "becoming an adult", my life was functionally the same in all other aspects. I didn't behave or seem more "mature" either really. Just looks.