While I am not religious person, I decided Lent would be a good time to give up Diet Pepsi. I was drinking three or four a day, and I had been reading a lot of information about aspartame and how negatively it can affect some people. The headache I encountered lasted several days and I was not sure if it was due to the caffeine shortage (I'm not a coffee/tea drinker) or the lack of aspartame. Since then I drink regular soda and I have gone through periods where I will have several a day on a regular basis. When I cut back to virtually none I have no headache to speak of, yet the caffeine deficit is still the same as with the Diet Pepsi. Therefore, in my situation, I can only believe that my body does not tolerate the aspartame well. As for weight loss, my biggest contributor is alcohol not soda, but I do know when I drink more soda I crave more things like crackers and chips.