Your explanation is correct for some babies with fussiness and 
gassiness.  The answer is to get more hindmilk into the baby and this 
can be done in several ways.  The usual approach for "overactive 
letdown", getting more hindmilk into the baby.  This does not mean 
keeping the baby at the breast longer, but keeping the baby at the 
breast *feeding* longer--better latch and using breast compression.  Nor 
does it mean feeding only one breast/feeding which is no more rational 
than saying the baby *must* feed at both breasts at each feeding.  If 
the baby "finishes" one side (no more open‹paus‹close type of sucking), 
and wants more, he should be offered the other side.  There are other 
tricks.

Galactosemia is a whole different story and should not be in this 
discussion at all.

Jack Newman, MD, FRCPC