If you recall, not very long ago there was a great deal of fervor over a report linking diet soda to an increased risk of obesity. The story appeared everywhere; on the AOL homepage, in the New York Times, and yes, here on That's Fit. I'll admit, at first I was a bit skeptical; to me it seemed more like an issue of correlation than causality. At the time, there really wasn't any explanation for the statistically significant relationship between diet soda and obesity rates -- all that was known is that there was clearly some sort of link.

Since then, a number of studies have produced information to explain how and why there may be validity to this connection. Most recently, a Purdue University study published in the journal Behavioral Neuroscience revealed that rats that consumed yogurt sweetened with an artificial sweetener gained 20 percent more weight over time than rats fed yogurt sweetened with natural sugar.

Evidently, the artificial sweetener caused the body to falsely believe that it needed to increase metabolism to digest more calories than were actually contained in the yogurt. Then, over time, when the rats were fed sweet food that was also high in calories, they tended to overeat in order to compensate for what their body mistakenly perceived to be an insufficient amount of calories.