You may think you’re doing yourself a favor when you trade a can of aspartame-sweetened soda for the high-fructose type, but you’re actually setting yourself up for a big gut—plus diabetes. A pair of recent studies shows that artificial sweeteners may be “free of calories but not of consequences,” says Helen P. Hazuda, of the University of Texas’s school of medicine.

In one study, researchers assessed the diet-soft-drink consumption and waist circumference of 474 subjects over two decades and found that diet-soda-drinkers averaged 70 percent greater girth compared to non-diet-soda drinkers. And the more you drank, the worse it got: Those who slurped down two or more sodas a day averaged 500 percent more circumference. Abdominal fat has been liked to a number of health conditions, including diabetes, cardiovascular disease and cancer.

In the second study, scientists studied the relationship between aspartame exposure and glucose and insulin levels in mice and found that the critters chowing down on the artificial sweetener showed higher fasting glucose levels and equal or lessened insulin levels. What that means? “These results suggest that heavy aspartame exposure might potentially … contribute to the associations observed between diet soda consumption and the risk of diabetes in humans,” according to senior study author Gabriel Fernandes.

The takeaway: Sticking to water is your safer bet.