I started running in May of 2011, basically as a way to keep off 20lbs I'd lost. I read a 'couch to 10k' article in a women's magazine and just started doing it; almost on a whim.
I had never run before; I smoked from the ages of 18 to around 32 and quit when I felt the first signs of obstructive lung disease. I really felt like I couldn't breathe that well; much less run.
I had done two 5k's over the past year; and generally run about 3 times a week. I kept the 20lbs off effortlessly and felt really good about running. It's the perfect sport for someone who really isn't that interested in exercise. It's hard but quick; you generally only need to do it for about a 1/2 hr. I know everyone's metabolism is different but for me it has been truly an effortless way to maintain my weight and stay relatively fit. It's solitary which I like, you're not expected to interact with anyone or even talk to anyone really. It's totally cheap and portable, I bring my runners now when I travel and it excites me that I'm enough of a 'runner' to run elsewhere; along the east river in NYC, along the beach in San Diego, on a treadmill in Mexico City. I'm a runner, that's what we do.
An unexpected benefit has been the stress release; all that bs you've heard all these years is true! These day if I get home from work and immediately tell my partner I'm going running; he knows exactly what that means. It means that I'm going to spend 30-45 minutes restoring my mental health and that the time might well spare us an argument, partially induced by work/commute related stress.
When I tell people I'm running, they're surprised. I am not an athletic type at all. I often get the same response I used to give runners--"I HATE running"; "it's so boring", "it's too hard"--etc. etc. And I guess all that is true, until it isn't, and you find you ARE one.