Q: I weigh 155 and am a size 6 comfortably. How is that possible?

A: Size 6 is about average for a woman, I believe, and 155 pounds may very well be about average weight for your height, so there's your answer :) Even if 155 is above average for your height, you may be more muscular than average or your fat distribution be different from average so you can fit in size 6 comfortably.