Skinny does not necessarily = healthy

Options
Hi all. A few years ago, I dramatically lost about 50 lbs, bottoming out at a weight that was far below healthy for me. As I was dropping the pounds, and while I was at my lowest (unhealthy) weight, I would receive receive frequent compliments and questions along the way like this:

"OMG you look so good! What's your secret?"
"You are so skinny now! You look awesome!"

Physically, I felt awful. All the time.

I wouldn't wish my experience on anyone. I would usually respond briefly and awkwardly so as to avoid going into detail about what was wrong with me. The comments began to anger me, because of all the implications underneath... Did I not look good before? (I was never that big to begin with, and I had always looked really healthy). Why did everyone think I looked so much better on the outside, when I felt terrible all the time? Why did people I barely knew think it was appropriate behavior to comment on my body in the first place?!

I stayed within 10 lbs of that bottomed-out weight range for about a year and a half, then I gradually gained back the 50 lbs plus some over the following year and a half. Now I'm solidly in the "overweight" range again, and am taking steps to improve my eating habits and overall health.

However, being "overweight" now, I feel so much better physically than I ever did when I was super-skinny. During that time, the only people who thought my emaciated frame was a problem were my immediate family who were really concerned about me. Everyone else assumed all was great.

In summary, why do we think it's ok to comment to women on their bodies in the first place? Why do we assume thin = healthy?

I wrote a lot more on my thought process at the time on my blog here: http://suburbankitsch.com/2009/10/14/vanity-and-guilt/