Here is a really interesting study. It essentially shows that rats 
who are fed artificial sweeteners
consumed more calories when they were put back on a normal diet. Basically the authors concluded that "... products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes." Essentially the rats ability to tell when they were full was disrupted.
Be Well,
Mike Reid
Below is the abstract, you can also read the entire article here:
A Role for Sweet Taste: Calorie Predictive Relations in Energy Regulation by Rats
Susan E. Swithers and Terry L. Davidson
Purdue University
Animals may use sweet taste to predict the caloric contents of food. Eating sweet noncaloric substances
may degrade this predictive relationship, leading to positive energy balance through increased food intake and/or diminished energy expenditure. These experiments were designed to test the hypothesis that experiences that reduce the validity of sweet taste as a predictor of the caloric or nutritive consequences of eating may contribute to deficits in the regulation of energy by reducing the ability of sweet-tasting foods that contain calories to evoke physiological responses that underlie tight regulation. Adult male Sprague–Dawley rats were given differential experience with a sweet taste that either predicted increased caloric content (glucose) or did not predict increased calories (saccharin). We found that reducing the correlation between sweet taste and the caloric content of foods using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity, as well as diminished caloric compensation and blunted thermic responses to sweet-tasting diets. These results suggest that consumption of products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes.
Keywords: learning, energy balance, cephalic-phase responses, thermic effect of food
Behavioral Neuroscience Copyright 2008 by the American Psychological Association
2008, Vol. 122, No. 1
