I went from sugar colas to diet colas a few years ago. I mean I was easily drinking up to 2L of the stuff, EVERYDAY!
I was borderline diabetic and I was only 25yo. That change alone made 30 pounds disappear in 6 months.
Now I'm transitioning from diet cola to plain tea and black coffee. I'm getting tired of the bloating and heart burn the sodas give me. Plus I want to cut out artificial sweeteners completely.
Good luck on your progress!