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Weighty Wisdom by: Elizabeth
Jackson, M.S., R.D.
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PART THREE: Patterns of Growth and Weight: Untangling What’s
Normal from What’s a Problem
Information in Looking Beyond the Numbers - Part 2 will
be helpful in understanding this column. You may want to read
it first.
As an infant and toddler, my oldest son, Sam, always got noticeably
fatter before he grew taller. But even more striking, his
head got bigger first before the rest of his body caught up.
It took me a couple of growth cycles to figure out this pattern:
it was just the way his body tended to grow. He always looked
a little top-heavy during those periods. Yet on the growth
chart—weight-for-age, that is—he pretty much tracked
in the same percentile the whole time. (Now, at 17, even though
his curly hair is out of control, the rest of him looks completely
normal.) On the other hand, lots of children do the shooting
up part first—they get taller quickly and look lanky
for a time and then they fill out. Some kids do this when
they’re younger, or older, right before their puberty
spurt (either getting chubbier first or shooting up, then
filling out). How does your child tend to grow?
Lots of parents do have questions about their child’s
growth. Many have been writing in to the Weighty Wisdom
website lately with their child’s most recent height
and weight measurements and age, asking, “is this normal?”
or “is my child overweight?” Erika from Japan (!)
told me her daughter, age 6, is 53 inches and 71 pounds; Suzanne
from California was wondering about her 5-year old daughter
who is 48 inches and 60 pounds; a Bartlesville, Washington
mom also has a 5-year old daughter who is a bit shorter at
44” and weighs 59 pounds; a woman from a small town in
the South had concerns about her neighbor’s child who
is 4 years old and weighs 97 pounds. Can we tell with these
numbers if these kids are overweight? With this column, we’ll
tackle what’s normal and what’s not normal in regard
to children’s weight.
What does normal growth look like on the weight-for-age
growth curves?
We talked in the last Weighty Wisdom column about growth curves,
what they are and how they came about. So what does normal
growth look like on the weight-for-age or BMI-for-age curves?
Well, first we’ll tackle weight-for-age. Remember,
the first rule in assessing growth is to look at the pattern
of growth, not just a single measurement. The answer is
simple: normal growth typically follows a certain curve
(roughly stays within a percentile track) consistently, for
both weight and height. This was revealed in large research
studies in the 1970s. When fed in a nurturing manner (lots
more on this in later columns), children tend to track nearly
from birth in the same percentile, the one that’s right
for them. This means that if your child has been in the 25%
for weight since infancy, he or she is either a bit shorter
than average or a bit thinner than average. If your child
has tracked in the 95% curve, he or she is either on the chubby
side or tall and big-boned or particularly muscular. Remember,
these curves are just measuring weight without taking height
into consideration, so taller, big-boned, muscular kids (as
well as chubby kids) are always going to track in a higher
weight percentile than their shorter, smaller friends at the
same age. One exception: multiple birth babies who are small
at birth or preemie babies may cross growth curves in the
first year to year and a half—but these growth curves
typically look like a steady upward line which then settles
into the percentile the baby is supposed to be in.
But what about that kid growing in the 95% curve, or above
the 95%, but parallel with the top of the curve?
Government standards say this child is overweight—with
the implication that it’s not normal or healthy and that
something should be done about it. And what about the child
who has been growing very consistently—but she’s
under the third %? Her growth line might form a nice parallel
line under the bottom of the growth curve, following it very
nicely—yet she’d be labeled as “underweight”
and a health professional monitoring this child might want
to do a work-up for failure-to-thrive. In both these scenarios,
what’s important is that growth has been consistent,
meaning that these particular kids at or above the top and
at or below the bottom of the weight-for-age growth curve
are growing perfectly normally. A later column will address
whether kids at the 95th % and above tend to grow up to be
obese (the quick answer: often not). That, of course, is the
fear behind the official declarations to do something about
these kids early.
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for larger view of normal charts |
high
/ fast
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average
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low
/ slow |
So then what does abnormal growth look like on the growth curves?
If a child is rapidly crossing growth curves, either upwards
or downwards, it means there’s a problem — whether
the child ends up well over or at the top of the curve or well
under the bottom, or moves from the bottom to the middle or
the middle to the top. Inconsistent growth is a reflection of
a problem. Remember, one measurement, whether extreme or absolutely
average, tells us almost nothing. If a child’s single weight
measurement is greatly above the 95% or greatly below the 3rd
%, a single measurement would raise a red flag because it’s
unusual and needs to be investigated. You would investigate
the situation by looking at the pattern of growth, as you do
to monitor any child’s growth. There are many reasons why
growth becomes dysregulated, meaning children gaining more weight
than expected or not gaining weight as expected or even losing
weight. We’ll discuss why this happens in the next column,
but a sneak preview: it’s absolutely not as simple as saying
that child’s had too much fat or sugar and not enough physical
activity.
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for larger view of abnormal charts |
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Now
what about those BMI-for-age curves that the Center for Disease
Control (CDC) created three years ago?
Remember, BMI is a comparative measure of weights at given heights,
so children of different heights and weights but with the same
BMI would (presumably) be similarly chubby or lean. These are
probably not used widely yet — and it may be a good thing.
I first heard about problems with the BMI-for-age charts at
a WIC (Women, Infants & Children, a supplemental food program)
conference, from WIC nutritionists who monitor hundreds of kids’
growth charts out in the trenches. They were reporting that
weight-for-age might be tracking beautifully in a certain growth
percentile for a child but the BMI curve often did not track
consistently. When plotting BMI, the measurement points bounced
around and did not stay in the same BMI percentile, making it
look as though there might be a growth problem.
I got a second opinion from Joyce Burke, RN, a certified family
nurse practitioner, who works with a pediatric family practice
group in Saginaw, Michigan. Her office vigilantly tracks height
and weight measurements to try to catch diverging growth early
before it becomes a problem. She said, that, in a mini-chart
review of some patients in her practice, all the kids were growing
consistently in weight-for-age percentiles. Yet only around
_ of those same children had BMI-for-age charts that looked
consistent; this agrees with what the WIC nutritionists were
noting. Why would this be? Well, think of my son: rounder body
and bigger head right before he grew taller...his BMI would
be higher right before that height spurt than it would be right
after! So, depending on when you take your child to the physician
for a visit, BMI could be up or down from the last visit. This
would make it appear that growth is problematic, and yet your
child might be growing perfectly normally. Therefore, always
insist that your child’s weight be tracked on the weight-for-age
curves, not just the BMI-for-age curves, so that you can keep
an eye on whether or not growth is proceeding consistently.
(Your doctor’s office stopped using them? You can get them
online at: http://www.cdc.gov/nchs/about/major/nhanes/growthcharts/charts.htm).
So what’s the answer for the moms and friends writing in
to the website about whether their child is “normal”
or “overweight?” The answer is that we simply can’t
really tell from one measurement. Most of the questions
concern kids in the upper weight percentiles — it would
make sense that these parents might wonder if this is okay.
They may even have health professionals pressuring them to “do
something” about their child’s weight. But remember,
kids can be growing normally even above the 97% if they are
basically following the growth curve. It’s those kids who
are crossing growth curves that might be having problems that
can result in abnormal growth. What about that 97- pound child?
Well, her weight is indeed so high that it would be pretty impossible
for her to have gotten there by 4 years old without a dramatic
upward turn on the growth chart. The neighbor mentioned other
issues that sounded problematic and indicated the child is undergoing
a lot of stress. I urged her to look into a professional evaluation
from specialists in her area. I hope the family can get any
help they may need.
The take-home message: if we support them in the right way,
kids will grow in their own unique way that is largely genetically
dictated. But if something’s going wrong with feeding,
children can indeed grow poorly, including gaining too much
weight.
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In the next Weighty Wisdom column, coming soon:
Why Do Children Gain Excess Weight?
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