Confused as to how often I need to exercise to lose weight

I'll just start by saying that I am not a personal trainer, but I will tell you what helped me lose some preop weight. I worked out at least four times per week, preferably five times per week. I did cardio only - walking and aerobics. Like you, I as not looking to build muscle at that point, I was looking to burn fat, burn calories, and shed pounds before surgery. Cardio does that for you.
Since you are trying to shed the last 12 pounds to qualify for surgery, I would NOT, NOT, NOT do any weight lifting, weight training, or resistance training at this time. Save that for when you're post-op. Weights and resistance training will cause you to build muscle, which under normal cir****tances is a "very" good thing. However, you will be building muscle and since muscle weighs more than fat, you might see a short-term weight gain due to your newly increased muscle mass. Like I said, under "normal" cir****tances that would be fine since everything would balance out in time. However, since you need to lose the 12 pounds for insurance approval, stick with the cardio for now and add in weights after you have your approval letter in your hot little hands.
I am not sure that I ever heard that "extra" exercise burns calories. Everything we do burns calories, even sleeping and breathing.
Good luck!
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