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. The researchers also found that thick liquids aren't as satisfying – calorie for calorie – as are more solid foods.

Based on the research, Davidson and Swithers suggest paying more attention to calories consumed and engaging in regular exercise to battle the bulge.

The Purdue's researchers' study, "A Pavlovian Approach to the Problem of Obesity," appears in the July issue of International Journal of Obesity. Davidson and Swithers, members of the Ingestive Behavior Research Center at Purdue, suggest that being able to automatically match caloric intake with caloric need depends on the body's ability to learn that the taste and feel of food by the mouth suggests the appropriate caloric intake. Much as Pavlov's dogs learned that the sound of a bell signaled food, people learn that both sweet tastes and dense, viscous foods signal high calories. This learning process begins very early in life and perhaps without conscious awareness, according to the researchers.

"The body's natural ability to regulate food intake and body weight may be weakened when this natural relationship is impaired by artificial sweeteners," said Davidson, an expert in behavioral neuroscience. "Without thinking about it, the body learns that it can use food characteristics such as sweetness and viscosity to gauge its caloric intake. The body may use this information to determine how much food is required to meet its caloric needs."

Over the past 25 years, there has been a dramatic increase in the consumption of artificially sweetened foods and low viscosity, high-calorie beverages, said Swithers, a developmental psychobiologist. "Incidence of overweight and obesity has also increased markedly during this period," she said. "Our hypothesis is that experience with these foods interferes with the natural ability of the body to use sweet taste and viscosity to gauge caloric content of foods and beverages. When you substitute artificial sweetener for real sugar, however, the body learns it can no longer use its sense of taste to gauge calories. So, the body may be fooled into thinking a product sweetened with sugar has no calories and, therefore, people overeat."

Swithers said that the loss of the body's ability to gauge caloric intake contributes to increased food intake and weight gain, especially when people do not count calories on their own. A similar dynamic is at work with foods' texture and thickness.
Davidson and Swithers' findings are based on two studies.

"Increased consumption of artificial sweeteners and of high-calorie beverages is not the sole cause of obesity, but it may be a contributing factor," Swithers said. "It could become more of a factor as more people turn to artificial sweeteners as a means of weight control and, at the same time, others consume more high-calorie beverages to satisfy their cravings."

The National Institute of Child Health and Development, National Institute of Digestive Diseases and Kidney Disorders, and Purdue School of Liberal Arts funded this research.

Source: Diabetes In Control.com.