Great to hear! I’ve been working at it about a half year now, and I’m still a true believer. Those walks you’re doing are a great way to start, and even for runners I think walking is important, because it’s such an effective, low-impact exercise for days when your legs are too sore to go fast–not that walking alone isn’t enough to see major physical and mental changes.
Like you, I’ve noticed the different body types in runners. I think there are few issues going on with those who still have weight problems that seem concentrated in their trunk. The first problem is that they may completely ignore resistance training, which is the best way to build and maintain muscle in your limbs. The second problem is that they may think running gives them carte blanche to eat anything they want, which is probably only true for serious athletes. And third, they may have the belly as a holdover from years on the couch before they started running. Right now I don’t look like a stereotypical thin runner either. I still have a bit too much belly fat because I haven’t lost all the weight I need to yet, but I also do heavy strength training, which means I will never be super skinny (not that I want to be). I do not believe that running is giving people beer bellies–even if running alone can’t always fix the beer belly.
It’s also possible to look very fat and have low visceral fat. Sumo wrestlers, for example, have huge rolls on their midsection, but it’s all at the sub-cutaneous level, since they burn all their visceral fat off with their vigorous exercise. They’re actually pretty healthy until they retire, when many continue to eat the same meals without doing the exercise. My dad is also physically health in his mid-60s, despite a huge belly, because he exercises regularly and (presumably) burns off the really dangerous fat around the organs. He continues to be so big just because he snacks constantly.
Big or small, I still think that daily activity is about the most important thing we can do for ourselves. I’ve second-guessed my views on diet many times, and often go back and forth on what or how much I should eat, but daily exercise has done nothing but good for my health, my confidence, and even my work and personal relationships. Exercise isn’t a silver bullet that will solve everything, but I think you’ll find your life only improves if you keep up your walks (and congratulations on your new baby!).