Even now, when "biking season" starts back up and I get out there, I'll be on the bike 1.5 hours or so. Every day if I can stick to it. Not shockingly, I lose a fair bit of weight during that time. Even without trying to do sprints or anything.
I'm sure I cheated some days and did the bus. But most days the walk was easier, as I didn't have to worry about timing and such. It was a crazy time, as I had given up on the gym and all other ideas, but that year I just dropped the weight like crazy. All because my car broke and I didn't have the funds to fix it. :D
(Of course, part of the "its been years" is that this is way more effective in your late 20s than it is later in life. At least, I think it is? Seeing how much time I was devoting to this, maybe I should try again. :D )
I suspect it is probably more than just an hours worth. Even today, if I build a habit of taking the dog on a walk around the neighborhood, that is probably a good hours walking on a single outing. I'm years from it, but I know I had to put in about 5 miles 1 way, which means I was probably doing 2-3 hours a day. And, again, I shed the pounds almost too rapidly.
It helped that it basically removed all of the time I would otherwise use to sit around and snack. :D