This is an interesting thread for me as I have tried to meditate to lose weight as well. I was cruising youtube last night and I came across this interesting video. I wasn't super impressed at first but at about 2:45 it got interesting. The lady on here talks about integrating change with your spirit.
http://www.youtube.com/watch?v=tK8GxmGona0
We can't stay on a diet because we have a certain mindset. Following this ladies videos it hit me that rather than put your body through the torture of diet, why not make it healthy by putting nourishing foods into and showing gratitude to it. This is stuff that I already know, but it hit home when I realized that by filling our bodies full of junk (including the chemicals that are in most processed foods) We are doing our bodies such a disservice. I am definitely going to try taking a new approach and combining it with meditations focusing on increasing the health of my body, and spirit. Good luck on your journey!