Don't I understand the feeling. I was actually at the low normal end of my bmi (for about 6 months) when that ulcer perforated (obviously, it was symptomless though they say eating more tends to help with duodenal ulcer pain, maybe I ate more subconsciously, who knows?) I was running to tone up, not a ridiculous amount, what a normal person in decent shape might run. I wasn't even weighing myself that often. Of course, I felt horribly overweight, but when they did the surgery they had to alter it some because of my having too much muscle and not enough fat in some area. I lost over 10 lb. in the hospital. That has got to be one of the worst, most painful surgeries a person can have. And now I'm thinner and wish I were thinner, but I can't get thinner, I have a pre-teen daughter, she already asks why I'm so small. Luckily, I eat normally, but it's the excessive exercise that gets me in trouble.