>There is a concept of "catch up growth" that is commonly believed in my
>circle of nurses and physicians.  I have NO documentation for this, nor have
>I searched for any.  The idea is a baby who has lost weight or gained
>inappropriately slowly over a period of time will temporarily gain larger
>than normal amounts of weight when adequately fed.

Catch-up growth is a well-established and documented phenomenon -- you can
find discussions of it in ANY book on childhood growth and development.  See
for example, "Fetus Into Man" by James M. Tanner (British physical
anthropologist, world's foremeost expert on children's growth and
development).  Catch-up growth continues to function until growth stops in
late teens/early twenties.

Humans have a number of genes that affect growth, including growth rate, age
at puberty, size at birth, presence of a mid-childhood growth spurt, etc.
The body will try to "stay on target" and can do so within certain limits,
depending on diet, disease, emotional distress, etc.  Anything that knocks
the growth rate of the child below its genetically-programmed growth
channel, such as insufficient diet, disease, cardiac problems, emotional
stress, etc., will result in lower than normal growth for that child while
the stress is there.  Once the stress is removed, the body will try to
"catch up" and get back on target -- so it will grow faster than normal as
it tries to do so.  Sometimes it "overshoots" its goal, and you'll see the
child growing much faster than normal for a while, and then slower than
normal as it tries to "catch down" to its appropriate channel.

This whole process is often called "canalization of growth" -- and both
catch-up growth and catch-down growth are well-documented.

You can see "catch-up" growth occuring in newborns who had small mothers
with uterine restrictions on prenatal growth -- the fetus slows down in
growth during the last weeks before delivery, and then grows by leaps and
bounds in the first weeks after delivery.

You can see "catch-up" growth occuring in young children who have been
diagnosed with growth hormone deficiency and started on treatment -- they
grow by leaps and bounds for the first few years on treatment, trying to
catch back up to where they should have been.  If diagnosed and treated
early enough, they will reach their genetic potential.  If not diagnosed til
mid- or late-childhood, they might not catch all the way up, but they will
certainly be taller than if not treated.

You can see "catch-up" growth occuring in families of immigrants to the US
from places with inadequate food, lots of disease, and/or emotional stress
(such as civil war and refugee camps) -- all the children start growing
better under better conditions in the US, and grow faster than normal for
children their age.  Those who are near the end of their growing years, say
those in their mid-teens, only have a few years to "catch-up" and will
therefore be only a little taller as adults than those who stayed in the
homeland or their parents who spent all their growing years in the homeland.
Those who are in mid-childhood will have more years to catch-up, and end up
taller than their older siblings.  Those are very young children will have
most of their growing years to "catch-up" and will be even taller as adults,
and finally, those born in the US who spend all their growing years under
good conditions will be just about as tall as the US average.  Thus, low
socio-economic status Mayan Indians from Guatemala and Vietnamese peasant
refugees who immigrate to the US will have children and grandchildren who
end up in height depending on how old they were when they came.  Those last
children of the family, born in the US, will end up the tallest.

Any physician worth his/her salt knows about catch-up growth.

Katherine A. Dettwyler, Ph.D.
Associate Professor of Anthropology and Nutrition
Texas A&M University

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