Sure, diet soda isn’t the sugar and calorie bomb of regular soda, but it’s not exactly harmless either. “Not only is there little evidence that diet drinks help people lose or maintain weight,” says nutritionist Marion Nestle, PhD, professor of nutrition at New York University and author of the forthcoming book, Soda Politics: Taking on Big Soda (and Winning), “but there’s some evidence that diet drinks cause similar metabolic problems to sugary drinks.”