My DD has always been at 75th for height and weight, but only really took an interest in solids at about 9 months, so was basically EBF until then. We have a friend with a baby who is about the same age, and hers has always been thinner and just a little shorter, like similar height but my DD is chubbier. Her LO can EAT, she puts my girl to shame. She's been eating solids, and a fair bit of them, for much longer than my DD, yet she's still thin. I think it's so silly to think that all babies should be chubby, not everyone is built that way! Some people are just built shorter and thinner, so of course their LOs will be smaller. As long as they continue to grow at an appropriate rate, I really don't think mamas with skinnie minnies should be worried at all.
Am I the only one with a tall and super skinny baby???? - Page 2
One of my sister's twins has always been on the tall side and almost alarmingly skinny so that you could count every rib (and the other one was/is a chunk-a-munk baby). But... she gets her genetics from her Mother (and the other from their Dad), and, she's always grow at an even rate, so the pediatrician has always told my sister not to worry about her growth, or her sister's growth, it's just the way each baby was made.
DS was (and still is) off the charts in height, but once he became mobile and all his baby chubs melted away, he didn't gain a single pound from around 12-24 months (in spite of eating like a horse--seriously, there's times he eats more than I do). I didn't worry about it because he was healthy, and always ate well. I figure we all have different body types.