I missed the original letter, so don't know what kinds of things have been ruled out.  I also don't know who to direct this to personally, so I'll put in my $.02 over L'Net in general.   Continued weight loss, despite a healthy diet and even pumping high calorie stuff, may indicate the development of a disease process.  The two that instantly leap to my mind are diabetes, and cancer.  Unfortunately, these leap to mind because I had friends succumb to each.  

Chanita, San Francisco