Hi there,
I exercise quite a bit so I don't know if this had anything to do with it, but I did lose all my weight by following the phase 2 plan. I am very careful about balancing my higher GI carbs with lots of vegetables & protein though. I snack on raw celery or carrots while I'm preparing dinner & really make sure that whichever carbs I choose are grainy & coarse.
It might be a question of experimenting & seeing what level GI your body can manage.