You absolutely can maintain a high TDEE with just walking alone. For example, if you walk for 8+ hours per day, as people do when thru hiking, you will struggl

You absolutely can maintain a high TDEE with just walking alone. For example, if you walk for 8+ hours per day, as people do when thru hiking, you will struggle to maintain bodyweight. Hikers spend a lot of time thinking about the most energy dense foods they can take with them to fuel their activity, which is low intensity but sufficiently high in volume that it drastically increases their energy expenditure due to activity. The description of your own experience is most simply explained by your usual diet putting you into a caloric surplus at your current activity levels, whereas when you were more active it was just enough to maintain or put you into a small deficit regularly.