Tips on how to start losing weight after a spine injury and surgery?

I’ve asked my doctor this question but he was pretty vague and said just walk. I’m curious how much I should be walking, if I can walk on a treadmill, if I should only do 10 mins at a time, etc. I’m doing some core exercises but I don’t think that’ll help me lose weight. I’ll call his PA to get more info, but I’m curious what has worked for those who have had surgeries / injuries.

I’m 9 weeks post-op from my microdiscectomy and just weighed myself. I have gained 30+ lbs since my car accident (when the injury to my back occurred) 1.5 years ago and I yearn to be active one day again. Before the accident I ran with my dog every morning, went on hikes, etc. All that stopped due to the debilitating back pain so I became very sedentary. And now 9 weeks post op I am still sedentary other than walking around my complex with my dog once or twice a day. I’m so anxious about reinjuring myself, especially since I’m dealing with a lot of sciatica post op still. Trying to balance being safe while also starting to lose the weight I’ve put on.

Any tips??