I was of course generalizing, but the point I'm making is that you need to get some (very) long term fitness goals. This usually drives you to find like minded people and action long term nutritional changes. You can get to a 5km within 5 weeks.
You have to remember that something like 40% of Americans are obese.
You're right, a 5k is pretty doable, but if you get to 5k and you don't find yourself enjoying it, you're never going to get to an ultra, but if you do find yourself enjoying it, it's much easier to work your way up to a 10k. And there's a lot of points between 5k and ultra where the game changes - a 10k feels different and has a different challenge than a half which feels different than a full (I can't speak for an ultra), and many of those points are perfectly healthy to stall at.
Long term goals are great, but only once you've set yourself on that path. The goal of running for a month and a half is enough if you've never run before.
