I suffer from Crohns disease - currently on Humira (though doesn’t seem to be working!).
I tried Huel as a way to get in extra calories during the day. Been trying to put weight on for quite a while, and weight lifting has helped a lot with that.
Whilst it’s going to be different for everyone, I can say that it didn’t seem to negatively affect me. Unsure as to whether it helped put any considerable weight on (I’ve been having powdered oats and whey protein shakes as well), but as it didn’t negatively affect me I continued with it, and about to order my second batch.
I think the main thing was that it helped to fill in the gaps between my morning meals, so that whenever it came to eating, I would always feel fairly full. I’m no pro so I can’t say for a fact that that would help to put weight on, but the logic works for me!
On a side note, a book that helped me with my diet for Crohns can be found here
Hope that helps!