Marg - I hear that too about being thin but I always go up 7-10 pounds and loose it and back up again. It was a lot easier when I had a cruise every 6 months so I had to stay thin to get in a bathing suit - now once a year it is harder to loose before the cruise.
Jut because you are thin doesn't mean it is any easier to loose or maintain...
I'm always on a diet too but I need to just change my lifestyle I guess and just not eat all those horrible things I have ocasionally but I have to splurge a little!!