I have the same problem you do (am clinically obese despite a relatively active daily schedule--I walk three miles a day, don't drink soft drinks, don't eat junk food, eat lots of fresh fruits & vegetables etc). I've come to a lot of the same conclusions, especially that insulin resistance probably has a lot to do with my problem. I switched to whole grains years ago (brown rice, whole wheat pasta, whole grain bread etc.) but my weight continued to creep up. These grains (along with others like bulgur and couscous) do make up the bulk of my diet, and my recent reading has led me to believe that the glycemic load of these foods combined with my own insulin resistance is probably what's making me fat.

I know you tried a low carb diet in the past, but you mentioned mostly eating turkey and bananas--bananas are a relatively high glycemic load food (http://www.lowglycemicload.com/index.cfm?ID=69) so that could explain why you didn't see much progress low-carbing it. (Low carb diets do work for me, but like the vast majority of people, I'm not able to maintain a diet based on such sweeping restrictions in the long term: and when I go off the diet, I quickly gain back the lost weight plus extra pounds.)

I'm taking the glycemic load approach now, which is a lot more flexible in terms of what it allows you to eat. (It's worth noting that there's a distinction between the "glycemic index" and the "glycemic load" charts, and that the glycemic load charts are much more useful for practical purposes.) I'm also supplementing with cinnamon and apple cider vinegar, both of which seem to have a beneficial effect on insulin resistance.

I'll try to put up another post in six weeks to report the results.