Diet soda might be calorie-free, but these artificially sweetened beverages could be linked to weight gain. This doesn't necessarily mean that you'll lose weight if you put down the bottle or can, however. Weight loss still requires burning more calories with physical activity than you consume through food -- so the most successful way to lose is to reduce calorie intake and get more exercise.
Diet Soda and Your Body
A study presented at the American Diabetes Association's 2011 Scientific Sessions followed 474 people over nine years. It found that subjects who drank diet soda had a 70 percent greater increase in waist size than those who drank no diet soda. The waist-size increase in those who drank at least two diet sodas per day was five times that of abstainers. While these findings don't prove that quitting diet soda will cause weight loss, they do suggest that quitting could help prevent future weight gain.