I had two bad knees and hips when I had my RNY over 10 years ago. I had limited mobility so didn’t do gym or a formal routine but I did make a point of moving as much as I could. I would get up every commercial and either walk around the house or dance in place. I cleaned like crazy just to get movement in (& fill in the space I used to use for eating). You can lose weight post op during the honeymoon stage without lots of exercise HOWEVER use this time to get into exercise habits and good nutrition as the honeymoon will end and you can regain very easily if you don’t have a good plan in place and go back to old habits.
I lost my weight without “upping” my exercise. I worked for a preschool and we took our kids on walks, did lots of dancing in the classroom, and since we had the room I was always the adult that helped them to set up and do obstacle courses in the yard or classroom. I also continued to help take our local scouts on long hikes and canoeing trips. All things I’d done before surgery. Now, I sit at a desk and am needing to get more exercise.