A large scale study has found that children who are slow to gain weight when they are babies often catch up with their peers.

Around 507 children were found to gain weight slowly during the first eight weeks grew up pretty quickly and had normal weight gain by the time they were two years of age. Another 480 children gained weight slowly up to seven years of age but had caught up with their peers when they turned 13 years old.
“In the past, a lot of parents have been caused a lot of unnecessary anxiety by health professionals and this is a positive and reassuring message. The second point for health professionals is that for a child that is well with no symptoms they can be relaxed and not worry about pushing calories because you can push them the other way”, lead researcher Professor Alan Emond said.
Source-Medindia