I lose about 10 to 15 lbs the first month in a flare and then it tapers off. I do regain the weight (wish I didn't) but my GI doctor said it is better for me to have a few extra pounds on me. If too skinny before a flare I wouldn't have the stamina to fight this disease. I am 5 ft 3 in and weight between 125 and 130 now. Was down to 123 and as high as 141. When I was younger I weighed about 110.
FYI birth control pills make you retain fluid, so therefore the extra weight when on them.