This is interesting. Several recent studies have linked artificial sweeteners with weight gain, which I find baffling and counter to my own experience. The rationale used to explain the phenomenon is that just the sensation of a sweet taste provokes an insulin surge in anticipation of sugar just as a ringing bell associated with feeding caused Pavlov's dogs to salivate. The insulin then promotes fat storage.
A new study from Purdue University seems to confirm that using artificial sweeteners makes it harder, not easier to lose weight. (Here's a link to the article, "Low Cal Sweeteners Tied to Weight Gain": http://www.smh.com.au/cgi-bin/common/popupPrintArticle.pl?path=/articles/2008/02/24/1203788130770.html)
The scientists fed yogurt, sweetened with either saccharin or glucose, to rats and discovered that the ones who got the saccharin went on to eat more and gain more weight and body fat than the ones who were given real sugar. The researchers speculated that the sweet-tasting foods prompted the body to prepare for a lot of calories, but when the extra calories failed to follow, the body was confused, which may have led to eating more calories or expending less energy than normal.
Herein may lie the explanation for why those of us who are on low-carb diets don't react like the rats in the study. If the expectation of calories is the causative factor, and the calories don't materialize, the rats over-eat. But what would happen if the sweet taste were accompanied by plenty of calories from fat and protein but not from carbs? Would you have happy, satisfied rats consuming lots of calories that can't be stored as fat?
I'm not a scientist, so I'm clearly out of my comfort zone here, but I'd be interested in hearing from some of you who are perhaps better qualified than I am as to what you make of this study.