A recent study has reportedly suggested that compared with sucrose, some nonnutritive sweeteners (NNSs) induce greater weight gain in Wistar rats. Fernanda de Matos Feijó, et al., “Saccharin and aspartame, compared with sucrose, induce greater weight gain in Wistar rats, at similar total caloric intake levels,” Appetite, November 2012. After feeding 29 male rats a free chow diet and yogurt sweetened with sucrose, saccharin or aspartame over the course of 12 weeks, Brazilian researchers found that “addition of either saccharin or aspartame to yogurt resulted in increased weight gain compared to addition of sucrose,” even though total caloric intake was similar among groups.

“Although saccharin and aspartame promoted relatively fewer calories from yogurt intake when compared to sucrose, increases in calories from chow intake effectively compensated for decreases in calories from yogurt, in such a way that there was a similar total caloric intake among all groups after the 12-week period of the experiment,” concluded the researchers, who speculated that the weight gain involved a decrease in energy expenditure or an increase in fluid retention. “However, it was surprising to find that the NNSs were able to induce weight gain without an increase in total caloric intake, suggesting that other mechanisms such as decreased caloric expenditure may occur after NNS use.”