According to researchers from the University of Texas Health Science Center San Antonio School of Medicine, aspartame and artificial sweeteners found in diet drinks are associated with expanding waistlines over time. The same has been found in the past with 'diet' snacks like cookies and candies. The researchers suspect that diet beverages in particular may give individuals a false sense of freedom when it comes to food, making them think they can have more of something else in place of a regular soda. They also believe that the sweet taste tricks our brains into thinking we're having sugar, which releases other hormones that may work against us, making us hungrier in the end, causing us to eat more.
While this research raises a very valid point, it is safe to say that the results of the study are not causal. Diet soda, which contains zero calories, does not cause weight gain in and of itself. It is very possible that the issue at hand is a behavioral one, whereby people's attitudes and opinions about food and their diets change by ingesting diet drinks, which leads them to take in more calories than they expend, which finally causes weight gain.
Ultimately, if you want or need a soda and your weight is of concern to you, you're better off choosing a zero calorie beverage over a sugar-laden 100+ calorie soda. If artificial sweeteners give you the heebie jeebies, don't worry - there are plenty of healthy options out there in place of diet sodas to help keep your waistline in check! Try sticking to plain old water,tea or coffee or spruce up your water with fruit or cucumber slices or maybe some mint leaves. The possibilities are endless.