Michael J. Fox was 27 in Back to the Future Part III when he played the character 'Marty McFly / Seamus McFly'.
That was over 34 years ago in 1990.
Today he is 62, and has starred in 69 movies in total, 49 of those since Back to the Future Part III was released.
In Back to the Future Part III, I think Michael J. Fox looks: