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.
Our attempts to fool ourselves are defeated because the parts of our brain that regulate appetite can monitor signals that provide an indication of how much calories were consumed.
"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.
"Historically, we knew that our body learns that if the food is thick, such as whole milk, it tends to have more calories than compared to a thinner liquid such as skim milk," Swithers said. "Now, our research reinforces this and takes it one step further, showing that our bodies translate this information about perceived calories into a gauge to tell us when to stop eating."
Two studies on rats yielded results that led to this theory.
Davidson and Swithers' findings are based on two studies.
In the first study, two groups of rats were given two different sweet-flavored liquids. In the first group, both liquids were sweetened with natural high-calorie sweeteners so there was a consistent relationship between sweet taste and calories. For the second group, one of the flavored liquids was artificially sweetened with non-caloric saccharin so that the relationship between sweet taste and calories was inconsistent.
After 10 days of exposure to the flavors, the rats were allowed to eat a small amount of a sweet, high-calorie chocolate flavored snack. The researchers compared the two groups' ability to compensate for the calories contained in the chocolate snack. The rats that had experienced the inconsistent relationship between sweet taste and calories were less able to compensate for the calories contained in the snack and ate more than the rats that had experienced the consistent relationship between sweetness and caloric intake.
"This suggests that experience with the inconsistent relationship reduced the natural ability of the rats to use sweet taste to judge the caloric content of the snack," Swithers said.
In the second study, two groups of rats were given a high-calorie dietary supplement along with their regular food every day for 30 days. Although the supplements were identical in calories and nutritive content, they differed in viscosity. For one group the supplement had the consistency of thick chocolate pudding, whereas for the other group, the supplement was similar to chocolate milk. Davidson and Swithers found that over the course of the study, the rats given the milk-like supplement gained significantly more weight than the rats given the more viscous, pudding-like supplement.
"This finding indicates that rats are less able to estimate and compensate for the calories contained in liquids than in semi-solid foods," Davidson said. "If the body is less able to detect and compensate for calories contained in liquids, then intake of high-calorie beverages compared to semi-solid or solid foods could increase the tendency to gain weight."
There are a couple of obvious lessons here. First of all, do not use artificial sweeteners. Second, drink water and get all your calories for semi-solid and solid foods. This is wise advice for other reasons anyway. You are better off eating an apple than drinking apple juice because the solid apple has more vitamins, minerals, antioxidant compounds, and fiber. The same holds true for other fruits and vegetables versus their juices in the vast majority of cases.
|Share |||Randall Parker, 2004 July 02 02:36 PM Brain Appetite|