This app was mentioned in 2 comments, with an average of 2.00 upvotes
C25K Running Trainer (or any Couch to 5K trainer, really)
For the first time in my life, I ran for more than 5 minutes solid and eventually ended up doing full 5K runs without stopping, slowing or walking. I was never a fat kid, quite the opposite, when I was younger I was anorexic and never had energy. Eventually I started eating again and just went a little overboard. When I finished C25K, I had lost 55lbs changing almost nothing else. It did take longer than the # of weeks the app suggests, but that's because I kept falling off, but I'd get right back on and either set it back a week or so, or start over. Eventually I finally made it.
I stopped using the app and gained back 10lbs... it's time to hop back on and reach my goal of losing another 25.
The official app.
https://play.google.com/store/apps/details?id=com.c25k2&hl=en