Which patients get skinny?

Hello,

I have a question that may seem a bit weird but might be important for deciding on further therapy:

Are the skinny Crohn’s disease patients usually those who had surgery? Or might they have had a massive weight loss because of other factors, like malabsorption and diarrhea due to the inflammation?

In other words: is it common to lose much weight although no surgery has been made yet?

I'm not only asking about your personal experience but also about what you have seen and heard from others.

Thank you!

Edit: The person in my family is very skinny and doesn't gain weight although she eats quite a lot. And we don't know why. No diarrhea, no throwing up, no loss of appetite. She didn't have surgery.

Edit 2: It’s even not sure if she has Crohn’s or ulcerative colitis. Because of the weight loss she thinks it must be Crohn’s. The doctors stick to UC but can't explain the weight loss.