I'm lactose intolerant but used to have a little milk in tea. I had to give that up, though, (along with peas) when I had a colicky son. Growth charts are just averages and babies are all different. Birth weights depend upon how much fluid has been swallowed - and whether anything was recently passed. It's perfectly normal to lose weight (fluid) then regain it in the first week or so. One breast is enough - as twins are successfully breast fed. A colicky baby will often be more active and sleep less, so will be using more energy than a relaxed child. We are a lean and healthy family (both sides) so, of course, our children are lean and tend to be tall. We have cow's milk allergy in the family - so wouldn't want to risk using formula. There's no need to, as, with frequent feeding, the milk supply should match a baby's needs. Bear in mind that fat or obese babies are not necessarily 'thriving' and may have future health problems due to overfeeding.