J.,
i have to agree with all the other moms here...1st, and MOST importantly, if your child isn't losing weight, and everything else is considered healthy to the dr...then don't worry! 2nd, yes go by your family...if most are thin, then most likely, your son will be too. and 3rd, giving ice cream from time to time is fine, maybe even after dinner every night...but 3 x's a day is just ridiculous! my daughter is 18 months old, and probably somewhere around 35 lbs...but she's ALWAYS been 90-100% on that chart. she's also VERY tall, she looks like she's 3 (even taller then my friend's 2 yr old, and just about the same height as my other friend's 2 1/2 yr old who btw is also big for his age!). the one thing that wasn't mentioned in detail is the metabolism. you have to realize, the more you eat (and specifically MORE OFTEN, not in eat meal) the more, and harder your metabolism works, especially when you're very active! mine is completely shot, the only time mine works is while and right after i eat...so dr's are telling me to eat 5-8 meals a day (same amount i would normally eat in 1 day, just split it up amongst 5-8 meals). last year, my daughter was eating about 6-8 times a day, and once she started to get around on her own, she ate about the same, just picking and grazing as the day went by, and she was pretty thin (for 1/2 of my family). and now, she eats about 4 times a day (1 time is usually pudding with my MIL which she gives even when i say no) and my daughter has started to pudge up! she's also shooting up in height, but she's got those chunky "thunder" thighs (at the moment it's cute, but if she keeps it up, she won't find it so cute when she's older) and she's got that pot belly, that makes her look fat, but she'll have it 1 day for a couple days, maybe a week or so, and then for 2-3 days she'll look REALLY thin (for her). i guess all this has to do with metabolism, how much, and when they eat, and genetics. if you want to try and fatten him up because he's considered "under" weight...try feeding him later, don't give him anything that is fat free, light, or whatever...make it all stuff like WHOLE milk products. there are plenty of things out there that can be healthy AND natural fattening. if you're feeling concerned about the dr labeling him under weight, and the way the dr wants to have you "fatten" him up...just get a second opinion. i'm sure he's perfectly fine. good luck.