Does Splenda hinder weight loss?

No, they dont. There is nothing within splenda that would alter, inhibit, or reduce metabolism or weight loss (unless you are using some rediculous amount, like 90 packets a day, which Im sure your not). You may want to look into altering some other elements, such as increasing your water intake, or varying up your exercise. Some people find that doing the same workout over and over again, there body begins to get used to that workout, and isnt facing as much of a cardiovascular work load. Either increase the workout difficulty, or increase the variability. Another thing I have found is even if I do a good solid 2 hour workout, I may spend the next 22 hours on my butt doing nothing. While doing those 2 hours I was very active, the lack of activity really hinders me throughout the day. Thats why pedometers are very useful, such as FitBit or Nike's products. They help keep you honest when your not working out as frequently.