Although they say it is the caffeine that causes it all, I really do believe it's the sweetners we use. Sweteners and sugar chemically act the same in the body--your body can't tell the difference since they both taste sweet. So every time you have a diet soda or something with sweetner, you body is getting the message "sweet" and your insulin and LH levels spike, putting you in a stall if you use them many times a day.
I know for me, this is very true and I use artificial sweetners very rarely or when there is nothing else.
Now, we all know you can't go through life with out it completely, I have developed a taste for Stevia--a plant based sweetner that is usually sold in health food stores and is packaged the same as regular sweetners are. Stevia is 300 times sweeter than sugar without the sugar spikes or chemical reactions. It is usually sold cut with chicory root to act as a filler because it is so powerful and you need so little. I use a brand called Touch of Nature--I take a few packs in my purse and if I go out for coffee, I have it with me. I have also bought it in bulk to do my cooking with--made a lovely cheesecake with it once and it was divine! I find that not using regualr sweeteners or sugar, I have less headaches, jitters, or heart palpitations which so many people have associated with coffee.
Hope this helps you in some way