Choosing a diet soft drink over a regular, sugar-packed beverage may not be the best way to fight obesity, according to new research from Purdue University. But the researchers said this doesn't mean you should grab a regularly sweetened soft drink instead. Professor Terry Davidson and associate professor Susan Swithers, both in the Department of Psychological Sciences, found that artificial sweeteners may disrupt the body's natural ability to "count" calories based on foods' sweetness. This finding may explain why increasing numbers of people in the United States lack the natural ability to regulate food intake and body weight.