Metabolism Help!!!

One of the worst things I can't stand about by weight is my lack of a good metabolism. I can train for weeks but I'm one of those people who has to consistantly stay at it too see results. I'm in a real need for a high quality metabolism booster that works. I'm obviously sick and tired of working so hard with no results. Being a former athlete it's tough to see my body go through this. I guess I could diet better!! Any thoughts?