I cannot recall ever reading Matt Stone say that weight loss was a sure thing following his plan. He has always said it MIGHT happen and that health is better than being thin in the way that media portrays. I did gain weight but that was coming off a too restrictive diet that I should not have been on in the first place. My weight gain has halted and I have gained a lot of muscle (I lift a lot), but no more weight, so some of that must be a swap.
the previous comments mentioned gokaleo and health at every size, they are great references