NEW HAVEN, CONN. — Several studies in recent years have found that low-calorie sweeteners disrupt metabolism and aid in the development of diabetes and obesity. Others have found that consuming low-calorie food and beverages has little impact on metabolism and promotes weight loss.

New research from Yale University may help resolve these conflicting findings.

The study, published March 3 in the journal Cell Metabolism, found that people who periodically drank beverages with the low-calorie sweetener sucralose did experience negative metabolic and neural responses, but only when a carbohydrate in the form of a tasteless sugar was added to the drink. In contrast, people who drank beverages with low-calorie sweeteners alone, or beverages with real sugar, showed no changes in brain or metabolic response to sugars.

“The subjects had seven low-calorie drinks, each containing the equivalent of two packages of Splenda, over two weeks,” said Dana Small, director of Yale’s Modern Diet and Physiology Research Center and lead author of the study. “When the drink was consumed with just the low-calorie sweetener, no changes were observed; however, when this same amount of low-calorie sweetener was consumed with a carbohydrate added to the drink, sugar metabolism and brain response to sugar became impaired.”

The goal of the study was to test the theory that consuming low-calorie sweet food and beverages “uncouples” sweet taste perception from energy intake and diminishes the physiological response to sugar that could ultimately lead to weight gain and diabetes. The Yale study may provide evidence that this uncoupling hypothesis is wrong, researchers said. The findings instead suggest that metabolism is impaired only when low-calorie sweeteners are consumed with a carbohydrate.

“The bottom line is that, at least in small quantities, individuals can safely drink a diet soda, but they shouldn't add french fries,” Ms. Small said. “This is an important information, particularly for people with diabetes who shouldn't consume sugars.”