I'm not the one in my little family with an IBD, but I'm putting in my two cents anyway. My hubs, Doug, is heavier than I have ever seen him, a result of not being able to eat the "healthy" things. He's terrified of anything green (fiber) and craves it at the same time. Yes, when at his sickest (an almost complete obstruction) he lost weight, 30 lbs in about a month, but since high fiber is not a choice, meat, carbs and cheese (not lactose intolerant) fill up a lot of his diet. Not exactly condusive to a thin body. Also, in spite of a 6'3" frame, I think his metabolism was shot years before they diagnosed him and he still eats like a bird and gains weight.
Even if speaking from purely my perspective and if I weren't familiar with crohn's, I can tell you that a lot of medications and health issues can make a person gain weight. my first foster child (a male) went from a very skinny 130 lbs 15 year old up to almost 200 lbs due to medication, then ended up diabetic also. Myself, although not the same as an IBD, I have IBS and have a hard time with fiber also, and even during the days I make a lot of trips to the bathroom and my tummy hurts, I'm an emotional eater and will eat more. Plus, anyone who has a chronic illness and is tired all the time knows how hard it is to get out and move (exercise) when not feeling well.
I just had to say.
I understand.