Julian looks athletic in the final pictures, like a distance runner or triathlete. As a distance runner I have a similar body type too.

At the gym you'll see a wide array of body types. Lean and mean, all the way up to muscular and bulky, and all things in-between. Body builders are HUGE compared to me and can lift far more than I can, but I can absolutely "destroy" them on a treadmill. You tend to discover the thing you like doing, specialize in it, and dominate it. What you choose to do partially dictates what you'll end up looking like.