"Diet Soda"

Researchers from the University of Texas Health Science Center San Antonio examined data from 474 participants in a longitudinal aging study and found diet soft drink users had a 70 percent greater increase in waist circumference compared to non-diet soda drinkers. The waist circumference increase was even worse for frequent diet soda consumers drinking two or more a day. Their waist size increases were 500 percent greater than non diet soda drinkers in the study.
“Data from this and other prospective studies suggest that the promotion of diet sodas and artificial sweeteners as healthy alternatives may be ill-advised,” said one of the researchers, Helen Hazuda, professor and chief of the Division of Clinical Epidemiology in the School of Medicine. (Source: Sciencedaily.com)
A related study found aspartame might increase blood glucose levels and thereby contribute to obesity.
One reason individuals give for drinking diet sodas is that they contain fewer calories, but then they reason incorrectly they should be able to eat even more than they would if they were drinking regular sodas. A better choice would simply be to not assume that drinking either type of soda is necessary.
Another assumption appears to be that diet soda is healthier, but if the research cited above is correct, it is not.
Sodas might also interfere with the absorption of calcium due to the phosphoric acid content, an effect that could also be caused by the caffeine content. In a different study, colas with and without caffeine both were associated with lower bone density. Phosphoric acid also erodes tooth enamel.