I don't see the problem with the commercial. When I put on weight after my daughter was born and after being on Paxil for a year, I was wearing size 12 jeans and was MISERABLE. I felt tired all the time, I felt so fat I didn't want to leave the house, and I was just totally disgusted with myself. I had always worn a 7 or 8, but for some reason I felt HUGE at a size 12. Well, I began eating low carb and lost 60 pounds in about a year. I got to my goal weight/size within 6 months and the weight just kept coming off. Even though I had never worn anything smaller than a 7 since my mid teen years, my size 7 and 8 jeans began to literally fall off. I've been a size 2 in jeans now for 2 and a half years. Even though I didn't think I could weigh 125 as an adult (I'm 5'8" and always weighed around 145), I feel SO much better, healthier, and more energetic than ever before, and I don't ever want to weigh over 130 again. So it IS possible to be a smaller size than you ever thought you could be.
My only other comment is to those of you who seem to resent people who feel "fat" in a size 8 or 10 or 12 - why does that bother you? Just because that's not YOUR situation doesn't mean it's not a valid concern for other people. I felt like an absolute cow in a size 12, and I was so terribly unhappy with my body. You shouldn't invalidate other people's feelings just because you might think there's nothing wrong with a size 12. For ME, 12 was totally unacceptable - and frankly, NOW a size 5 or 6 would be unacceptable as well. And there's nothing wrong with that at all.