Your post touched me because I think that a loss of an attraction was a major factor in my divorce. Like you my ex and I were best friends for a long time. but, as time went on my ex "aged", and not just "physically", she aged "mentally" as well. She got to teh point where she was just "frumpy".

She did very little to make herself more attractive and was very uncomfortable with her body and her sexuality. As a result she did become less and less attractive to me. Not that she was an "unattractive" , woman, she was not.

Since my divorce I have dated women that were not beauty queens but they had an air of confidence about them, they did things that made themselves more feminine and attractive and they were open with their bodies and with their sexuality. That made them more "attractive" to me. So it is not just about looks, or weight (although it sounds like weight may be a contributing factor in your case). It is about attitude and confidence and sensuality... the whole package.