S was about C's age when he was diagnosed, so starting from the point of coming off a flare, S has gained weight in spurts. As he'd lost 20-25 lbs pre-dx, he regained that weight fairly quickly while on exclusive and then supplemental EN. Then, over the next couple of years, he gradually gained another 20 lbs, but it was in spurts, 10 lbs then nothing for a few months, then 5, then nothing, etc. (There were even periods when he'd lose a pound or two but I saw that as normal weight fluctuation.) But, throughout this period, he was taking in 1500 cal/night (5 nights/wk) of formula, plus three normal meals per day.
Since starting remi (approx. 1.5 years), he's stayed on 250-500 cals per day (1-2 Boosts) and gained another 5-8 lbs.
He hasn't had a lot of height growth, 1-1.5 inches, but he was already 5'10" at dx. Once he regained the lost weight, plus the first extra 20, he's really just filled out. ie developed less a boy's body and more a man's. It certainly hasn't been 'flabby' weight gain.
Perhaps, something for you and C to consider is that the reason to continue with supplemental EN isn't strictly for 'pounds' but that the calories PLUS the
nutrition will help his body during the coming transition from boy to man. Whether or not S's continued use of supplemental EN has helped control is crohns is possibly up for debate but, I have no doubt the nutrition has done nothing but help his health in a general sense and any growth/development is dependent and a reflection of underlying health and nutrition.
Just my thoughts...