What does WLS do to our metabolism?

Coming to this post late, but you voiced a concern that I too have been feeling lately.  I have been thinking a lot about having my thyroid levels checked out.  At 2 years out, it is near impossible to loose weight, even when I am tracking all my foods and eating less than 1000 calories a day.  

I have wondered if it is just the case that I am much lower in weight than I ever was and it is just harder to lose weight when you are thinner?  Do regular (by that I mean non-WLS people) have the same experience?