One time I lost 10 or 12 pounds in a month, which may not seem like too much but when you weigh about 110 or 115 to begin with, as I do, it's pretty noticeable. The reason for the weight loss was some medication I was on which caused it as a side effect. Fortunately I eventually regained the weight.

I do imagine changing one's eating habits would be difficult, so props on that! I uh... I don't care how much I weigh so I eat whatever I want. I eat a lot of junk food. :x So far this hasn't caused any ill side effects, and I'm a pretty standard healthy weight-- probably a combination of getting lucky with genetics/metabolism and the fact that I move around a lot at work-- but I have this fear that it's going to catch up to me some day in the future.