The message seems obvious, but when popular culture focuses fiercely on youth and the appearance of health and fitness, identifying how looks and lifestyle each affect attractiveness is not so simple. To some degree, the idea that youth is more attractive assumes people are also more active when they are young. Considering how many adult lives involve commuting to a desk job, there is a grain of truth to that, but it's hardly set in stone.
More to the point, people of any age who sit watching the latest "reality" TV show seem less attractive than they would discussing their favorite music, playing Trivial Pursuit, walking the dog, or planting a flower bed. It's also not a competition. You don't have to win marathons or qualify for Mensa to be an attractive person.
As best I can determine, both mentally and physically, active is attractive!