I just signed up to do a 5k in October. I'm insane.

I did my first 5K pre-op at 350 lbs, and did it in 49 mins You can certainly do this in October.

My advice is to just start walking regularly - slowly increasing distance. It's just important to keep walking

Congrats for signing up - you won't regret it at all!!

I was curious how long it would take me to walk the mile loop in the neighborhood, I usually just putter around out there for 30 minutes but never measured the distance. We did the mile in 25 minutes (I drug the cranky kids with me). Not too bad, didn't even realize I was walking that far Feels great to have all of my lung capacity and energy back! Having food and vitamins helps LOL

First off, congrats on registering for the 5k! 

Honestly if you cannot walk 3 miles by October, there is something seriously wrong.  You will be amazed what your body can do with increased demands.  Walking is so simple and easy, you should be walking 3 miles EASILY in a month. 

Walk your neighborhood and every 2 weeks or so, I would recommend heading down to Town Lake...park under the Mopac bridge and walk down to the Lamar bridge and turn around.  That route  will be about 1.75 miles.  When you feel more capable, walk the first loop, crossing Lamar and by the time you get to your car, you will have gone 3 miles.   You can do it!!! 

I vote you consider running a portion of your 5k...screw walking it...you will master than way before October!   Push and work that new body!  ;) 

Yes, back in the day when I was just overweight, I could do five miles in about an hour (but this was in Hawaii where it's not 900 degrees outside and I was young too). I know I can do... I just have to work up to it. I think it'll be fun :)