Mmm, I mean yeah depending on what you add Subway isn't so different from any other fast-casual place nutrition wise. Though, with an introduction of moderate cardio to this guy's lifestyle it shouldn't be too hard to burn off a single sub. Hell I love the meatball sub with veggie fixin's, especially when they still had 5 buck footlongs.
I eat at Subway a lot but it's not "healthy" at all since I always order a lot of meat with extra cheese, bacon and zero vegetables. In fact I probably make it even more unhealthy than the average fast food joint.
Good he can use this a motivation, to go to the gym and after a year he'll look like a chad. Remember let it forever play in your head again and again. Of how you were embarrassed, disgraced and humiliated.