Humans seem to have a genetic target for growth -- a genetically-based
"channel" or pattern of growth to which the child strives to match. Various
environmental circumstances, both in utero and after birth, can lead the
child to fall below *or above* the target channel that the genes are
striving to match.
Sometimes an environmental constraint -- such as a small mother/uterus
before birth, or lack of food in infancy or lots of disease in infancy --
means that the child falls below their targeted channel. When the
environmental constraint is removed -- such as being born removes the
constraint of a too-small mother/uterus, or food becomes available or child
grows old enough to demand more food or steal it from their younger
siblings, etc., or the child survives all the viral diseases of early
childhood and doesn't get sick so much anymore -- then you may see
'catch-up' growth where the child grows faster than typical for his/her age
and may even overshoot the targeted growth channel. This is especially
apparent with children who have growth hormone deficiency. Once they are
diagnosed and started on treatments, they may grow as much as twice as fast
the normal rate, as their body desperately tries to match up the child's
current size with their genetic potential.
Sometimes the environment contributes to overgrowth of the child in utero,
often simply because the mother is large and so uterine size is not a
constraint. The baby is born larger than its genetic targeted size, and you
will then see 'catch-down' growth -- the baby grows more slowly than typical
for its age, as it tries to 'catch down' to where it is supposed to be.
This is also true for the child with hormone deficiency who grows super-fast
and overshoots their target -- they may then drastically slow down their
rate of growth, even below normal for their age, as they try to catch-down
to where they are supposed to be.
British auxologist (human growth specialist) James M. Tanner, wrote about
both catch-up and catch-down growth in his many papers and books about human
growth (search 1950-1990 for publication dates). Fetus Into Man is his
classic human growth textbook, fondly known to generations of students as
"Fetus Man".
All of which is to say, that no, one shouldn't *necessarily* expect big
babies to eat more than small babies. Big babies may eat even less than
average size babies, as they 'catch-down' to their normal growth pattern.
Also, while most intake calculations are based on kilo of body weight, human
variation includes vast differences in metabolism and activity level, so
that babies who weigh the same may need very different amounts of breast
milk or formula to grow optimally, while two babies of very different sizes
may need exactly the same. That is one reason why it is best to let the
baby be the one to decide how much to eat, at the breast, rather than trying
to use "one size fits all" calculations about so many ounces of formula per
ounce of body weight.
Kathy Dettwyler
Specialist in child growth, among other things
P.S. One anecdotal example using dogs. We had two litters of puppies born
to our average-sized golden retriever female, Roxanne. The father of the
puppies, Beau Geste, was a Great Pyrenees (giant white dog that looked like
a polar bear). The puppies, at birth, were standard golden retriever puppy
size, due to intra-uterine growth constraints. There were fewer puppies
than a normal golden retriever litter, but more than a normal Great Pyrenees
litter. Usually, Great Pyrenees puppies are quite large at birth, compared
to golden retriever puppies. These cross-bred puppies were not intermediate
in size at birth, they were golden retriever puppy-sized. The puppies grew
at an *alarming* rate, so that by six weeks of age, standard
weaning-and-giving-away time for puppies, they were about 1/3-1/2 the size
of their mother, much larger than golden retriever puppies of that age. If
she was standing up and they wanted to nurse, they had to duck down (which
they did). She, in contrast, was a mere shadow of her former self, as she
turned all her body weight into milk for those puppies. It took her about
six months to recover her normal body weight after the last of the puppies
weaned. As adults, the puppies ended up in size anywhere from smaller than
their mother (the largest puppy at birth) to bigger than their father (the
smallest puppy at birth). Most were in-between the parents in size.
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