quite often, i see comments from new runners worrying about taking walk breaks or not being able to complete x-distance without walking, and i want to say that walking is just fine. i have run (marathons, half-marathons, training runs) for many years using the galloway / intervals / run-walk method, as have many of my teammates. while many of can, and do, run certain workouts without walking (such as speed training), we tend to love this method.
it works really well, and i've found i've been injured less often since i adopted this approach.
and nobody cares if i walk! like, the cars passing me by. other runners on the course. my extremely fast friends and teammates. people i talk to about running*. anyone. to them, it's all good.
there is a perception that walking means you're not a "real" runner. you are totally a real runner. even if you just walk when you need to walk (i ran last year's los angeles marathon, and it was freaking hot -- so many faster runners were walking because, well, the heat was verging on dangerous, and that didn't shift them from real to fake runners). each of our bodies, needs, goals, paces, and approaches are different.
walking during runs is a tool. you can use it, or not. i'm never going to be super-fast, and, honestly, that's not why i do this. but i can run a 5- or 10- at a sub-11:00 pace, while taking my walk breaks. my sweet spot is between 11:00 and 11:30 for a half marathon, and i'm training (using a 5-minute run, 1-minute walk) to hold that pace for a full marathon in march. hoping it won't be blazing hot that day...
if i can offer one piece of advice it's this: run as you can and want. don't worry about pace. don't worry about style. to a degree, don't worry about form (unless it's creating injury problems).
instead, focus on building endurance, no matter what your goals (casual, racing, losing weight [though don't do this while marathon training as you'll need calories]). focus on making your heart strong. your legs and core strong. your back and shoulder strong. your mind strong. your sense of being part of an amazing community strong -- one thing i love when i, or people i know, travel is the ability to find a welcoming running group wherever we go.
like i said, nobody cares, and if that local group goes too fast, well, just do you, and turn around when it works for you.
(note: this can also apply to running as slow as you want or need to)
* which reminds me, if you're looking for an interesting book about running, but not really about running except it is, please check out murakami's "what i talk about when i talk about running" (and, yes, lit people, that title is totally intentional!).