I think most people know that soft drinks are bad for you. Refined sugar in large amounts is essentially toxic, and is the number one contributor to obesity (In my opinion, and called "white death" in the health food community). Phosphorus, sodium, and caffeine block calcium absorption, and caffeine is the most widely used drug in the United States. Soft drinks will kill you.
I've been reading a book called Skinny Bitch, by Rory Freedman and Kim Barnouin. They describe diet sodas in a no-nonsense way (similar to the rest of the book!).
Don't let yourself off the hook if you drink diet soda---it's worse than regular in many ways. True, it has no sugar, but in it's place there are chemicals. Artificial sweeteners negatively impact the signal system your body has with your brain regarding telling you when you are full and creates cravings for "sweet" foods. It's not all in your head, it's a chemical thing. Aspartame is a common one used, and this evil beast also causes arthritis, birth defects, fibromyalgia, Alzheimer's, lupus, multiple sclerosis, and diabetes. Not only that----the methyl alcohol in aspartame enters the body and turns into a cancer-causing compound called formaldehyde (yes, the same thing scientists use to disinfect things in a lab). When you consume aspartame in conjunction with carbs (in food or drink) it causes a decrease in brain production of serotonin (the happy chemical). Not to mention, if you're drinking soda, you probably are not drinking enough water.
Rory and Kim's question to you: Did you know your diet soda was making you fat, sick, and unhappy?!
Soda (regular and diet) is like cigarettes. You can smoke them today and feel pretty good---and even attribute the "good" to the cigarettes. However, you are causing your body to rot from the inside. I'm not kidding when I say you are rotting, but that's another topic for another post.
If you need soda to feel normal, you are addicted. If you can't function without it, your body is begging you to change. It's simple. Maybe you don't want to change yet---and that's your choice. I'm sure you have a justifiable reason for not doing anything differently. But when you're ready, the information is available to you.
My recommendation is to stay away from soda altogether. When I'm coaching, I don't project my opinions in an assertive way---it would make people angry, and a lot of the time, they aren't ready for the information because they are not ready to make a significant change. With soda, and anything else in wellness, you don't have to go from point A (drinking soda) to point B (not) all at once. In person, I probably wouldn't have given you all this info at once. But if you ask me, I will tell you---and someone asked me about diet soda this week. So there you go :)