A recently discovered hormone appears to control aspects of metabolism: whether the body is burning sugar or fat for fuel, for instance.
Here's an article about a recent study. The first link is the one I encountered first, apparently a reprint, in the course of researching the post about Tre Wilcox
Scientists: Hormone could shed new light on weight lossBy Sue Goetinck Ambrose
The Dallas Morning News, June 6, 2007
The link on the Dallas Morning News site
According to the article, the researchers say their work lends credibility to low-carb diets. It seems that when fasting, or when consuming a low-carb, high-fat diet, this FGF21 is produced, signaling the body to burn fat, including stored fat. The researchers says this could explain why low-carb dieters don't have excessive fat in the bloodstream -- because they're burning it.
The article refers to research done on rats. The researchers are quoted as saying that research with humans would likely be a promising avenue.
Here's an interesting quote from in the article. The speaker is described as "neuroscientist Randy Seeley, associate director of the Obesity Research Center at the University of Cincinnati, who was not involved in the research."
Still, Dr. Seeley noted, the discovery of the hormone alone shows how much scientists still have to learn about why the body burns or stores fat.
“The modern era of studying obesity started in 1994,” he said. “Do we have good treatments yet? The answer is no.”