Last evening our CBS-TV affiliate ran a short segment on the local news about a new understanding of the role serotonin plays in the body's management of weight. It seems serotonin can signal the brain to store food as fat or burn it as energy. The result was that different people can eat the same things and it turns to fat on one, but not on the other. They are hoping the new understanding might lead to more effective weight control tools.
I went looking on the Internet for more details and found only articles from the last few years on serotonin and weight loss.
If anyone finds a link to a story with more detail, please post it.