Good luck to you and don't be discouraged if you have to do the 6 month supervised diet. Many doctors in the United States are now instituting the six month supervised diets, nutritional classes, psychological testings, seminar's, etc. whether or not insurance companies require it. Their reputation is on the line and they want the best outcome. I have gone through it and the time goes by quick. I've been fat a long time and six more months isn't going to kill me and I lost 60 pounds in that time!
If you have to do the six months supervised diet, why not put 100% into it! Go low carb 40-75 - high protein, learn to not drink with your meals, learn to chew your food slowly and thoroughly. It's what this time is for. Surgery is a lot easier on you and more successful if you can start working on behavior modifications in advance.
I suggest signing up for http://myfitnesspal.com and logging in once a day to keep track of your water intake (try to get up to 64 ounces) track your food and calories and exercise. Can't exercise? Neither could I. I stood in place and walked for 5 minutes at a time and tracked it. I finally was able to fit on the Gazelle and could do 5 minutes, now I can do an hour and walk a mile and I haven't had the surgery yet.
The first time I went to a surgeon for WLS, I was became depressed learning about the six month diet. I ended up quitting. Second time I went to another doctor, and I couldn't write it all down, and I ended up getting pneumonia, and kept drinking orange juice and eating pretzels and even lied about what I was eating and quit.
By this time I gained about 60 more pounds for my third stint. This is a lifestyle change, not a diet or an easy-way-out, this is hard work, so I figured I would try working on changing behaviors now.
I wish you the best of luck.