I have had a lot of success with the Weight Watchers method. I want to lose around 18 kg and I lost already 12 since middle of October.
I think most people fail because they expect immediate results and can't stay consistent because they go too hard for immediate results. On WW when presented with an unhealthy meal option I would consider if it was really worth it giving how well I was doing, and I wanted to crush it on the scale every week. I think for me that was the most important driving force to not making bad decisions like eating a pile of cookies. People think they have to sit there depriving themselves with a pile of lettuce but that is exactly what WW discourages. You can eat whatever but it has a cost. For me I was happy eating lean good food like a small sirloin steak with some broccoli.