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
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 think the metabolism's feedback system just incorporates all that. You move more, you get more hungry. If you resist that hunger temporarily, the body signals low energy and sets the burn rate of something other lower (brain, fidgeting, body heat, immune system).