Tag Archives: growth charts

Catch me if you can

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Before my foray into the world of celebrities I was talking about babies, children and the effect that illness can have on their metabolism. I have also alluded to something called catch up growth and the fact that it might be important for the overall risk of obesity and chronic disease.

What is catch up growth? The medical dictionary defines it as:

“…an acceleration of the growth rate following a period of growth retardation caused by a secondary deficiency, such as acute malnutrition or severe illness…”

The easiest way to track catch up growth in visual form (and you know that I like my visuals) is on growth charts. Children tend to follow an individual growth curve, predetermined largely by genetics, and this phenomenon is called ”the canalisation of growth”. As we have established in the previous post, an illness or or a period of malnutrition may result in falling off the curve. Catch up growth is the body’s attempt to get back onto the original curve.

Growth curve flattening and fall (example only)

Accelerated growth during recovery phase

It has been known for quite a long time from observational studies that babies and children who undergo a period of catch up growth seem to be at higher risk for obesity and diabetes later in life. This was also observed in children born small for gestational age (SGA),  which is an indirect indicator of fetal malnutrition. Similar phenomenon was noted in children growing up in famines (the Dutch famine study) and the survivors of the Leningrad blockade in the WW2.

Studies conducted in the 60′s and 70′s looked further into the energy metabolism of catch up growth. They showed that the rate of growth in these children is astonishingly up to 15-20 times the rate of normal pattern. Moreover, this period was accompanied by both increase in appetite and increase in BMR in the order of 4-5 times the controls. It seems that when children were fed ad libitum they spontaneously increased their food intake to ensure their bodies get back on the curve. As their weight approached the expected measure for height their appetite would decrease back to normal levels.

Another interesting observation made around 1980 was that children do not regain lean body mass at the same rate as they lose it. Muscle recovery lags behind the recovery of fat tissue even when children regain their weight and get back on their growth curve. As one of the studies frames it:

“The impressive gains in weight made by recovering malnourished infants are largely fat; reconstitution of lean tissue does not occur equally well at all rates of weight gain.”

Let’s go back to some visuals or rather my illustration of the above.

Body composition changes during illness and recovery

The greater degree of the initial weight loss, the more unbalanced the pattern of catch up growth.

Later research started to elucidate the mechanism by how this imbalance occurs. Several studies have identified that the phenomenon of catch up fat is accompanied by hyperinsulinaemia, relative insulin resistance in skeletal muscles and hyperresponsiveness to insulin in adipose tissue.

Basically, when the child is recovering from a period of malnutrition their bodies produce more insulin for the same amount of glucose. Their muscles “shut down” the insulin gates and their fat tissue opens the gates wide so that glucose is shuttled away from the muscles and into fat.

Some of the more recent studies have tried to explain this phenomenon using terms like “thrifty gene”. Since no such gene has yet been identified to my knowledge I’m a little unconvinced. What interests me however is whether this slightly worrying pattern is diet-dependent. In other words, what do you feed a sick malnourished child to prevent this from happening? Is there a single dietary cause? What did all these children in observational studies eat?

Looking for causes in cohort data is always a fruitless exercise and a reminder that we should use it to generate hypotheses only. Randomised controlled studies on actual babies are obviously out of the question, I doubt there is an ethics committee on earth which would agree to withholding food from children and then watch them lose and then regain weight on various dietary regimens. There are always rats but they have an obvious disadvantage of being…well, rats.

One zealous study examined the rats undergoing catch up growth after semi-starvation. Those re-fed a high-fat diet were found to have more hypinsulinaemia, higher fat deposition and lower metabolic rate than the rats fed a low-fat diet. Both re-fed groups had worse metabolic derangement compared to controls. A closer attention to the high-fat diet tells you that the rats were fed 1:1 corn oil:lard mixture as 50% of their diet. What does it tell you? That it’s not a good idea to feed rats 25% of their diet as corn oil. Not much else really. It also makes it clear that both re-feeding diets resulted in higher insulin response to the same glucose load, higher adiposity, lower thermogenesis and other markers of disordered metabolism.

So we are back to generating hypotheses.

Recent developments implicate a group of messengers called IGFs, insulin-like growth factors. A series of experiments on none other than zebrafish showed that low cell oxygen level as would occur in malnutrition or disease can disrupt IGF signalling which activated the MAP kinase pathway, necessary for growth. Restoring oxygen to the tissues did not always result in full system reboot. Pathways other than MAP kinase may be activated which could explain the different growth pattern. Sigh… let’s wait for the zebrafish to give us the answer.

While you are digesting all of this info I will put together my take on some of these fascinating issues. Of course, I could be the only one who actually finds this stuff so intriguing and you might be going about your day without giving the concept of catch up growth a second thought. But I reckon some of this might still apply to you whether you are a determined bachelor or a mother of four. What if you were the one who had a prolonged illness at some point in your childhood? What if this pattern of metabolic disregulation also applies to the yo-yo dieters amongst us? Aha, now you are thinking about this.

Look out for my summary post on child metabolism in the next couple of days.

More reading:

Ashworth A, Milward DJ, Catch up growth in children (1986) Nutrition Reviews 44(5):157-163

Jackson AA, Wootton SA, The energy requirement of growth and catch up growth, Proceedings of an I/D/E/C/G Workshop held in Cambridge, USA 1989

Dulloo AG et al, Pathways from weight fluctuations to metabolic diseases: focus on maladaptive thermogenesis during catch-up fat (2002) International Journal of Obesity 26(S2): S46-S57

Ong KKL et al, Association between postnatal catch-up growth and obesity in childhood: prospective cohort study (2000) BMJ 320:7240

 

 

Gluttonous babies and other nonsense

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Children the way they are supposed to look

One of the highlights of my obstetrics rotation was a tutorial with a lactation consultant. I remember the conversation turning to the link between infant formula and future obesity. A medical student, a very intelligent and industrious girl, who will make a fantastic doctor one day, said: “The reason why infant formula causes future obesity is because a baby feels compelled to finish the bottle which is presented to him or her”. Too many calories and the habit to overeat makes Jack a fat boy. I don’t think this was one of her brightest moments. No judgement, we all have our bad days ( I did miss 4 cannulas today).

Funnily enough, I have heard similar sentiments quite a lot recently. We are all familiar with a “gluttonous sloth” theory of obesity. The cries of our public health authorities to eat EVEN LESS and move EVEN MORE are starting to sound a tad desperate. Considering that we are doing what they are asking us to do (for the analysis of the Australian Measure Up campaign please read here)… I have to admit though, I’ve never imagined that infants and children will cop the same admonishing finger.

The notion of caloric control is subtly penetrating the hitherto untouched area of infant nutrition. If Mummy is encouraged to weigh up her skinless chicken breast portion and count it into her daily caloric regimen, then why not her little baby?

Obviously, anybody who has had any contact with babies and children would know that they are unaware of our adult rules. Trying to stick a piece of meat into the mouth of a struggling toddler is something everybody needs to experience just for the fun of it. Amazingly enough, babies and small children cry and ask for food when they are hungry. Even more amazing is the fact that they will stubbornly squeeze their lips shut and shake their heads when they are full.

Newsflash: Infants say “No” to food when they are not hungry.

That is until their metabolisms are screwed up by foods like infant formula, sweets, fruit juices, biscuits and breads. The innate sense of satiety remains in children even if the bulk of their diet is made up of Coke, chips and lollies. “Do you want another grass-fed lamb chop?” Nope, full belly is displayed for visual confirmation.  ”Do you want some toast with vegemite (for non-Aussies, yes, our children really do love this black sticky yeasty spread)?” More often than not, you’ll get a yes.

As I’m about to publish this, I get the latest post from J.Stanton on satiation vs satiety. Looks like toddlers understand this concept much better than some adults.

So where do the problems start? Let’s say you have gone through the initial hurdles and now breastfeeding on demand, ensuring your baby develops a healthy gut, strong immune system and a smart brain (this bit may or may not come useful later). You may have already started some solids, introducing one food at a time, however the occasional spoonful which actually gets inside is unlikely to add much to overall caloric status.

Since you cannot measure how much breastmilk your baby is having, the secondary indicators of any baby thriving are weight gain, output (what goes in must come out) and energy levels. Here is where hit a second hurdle. To assess growth we use growth charts. How are growth charts designed? By collecting data on height, weight and head circumference from healthy babies, plotting them on a graph and allocating centiles (= equivalent to a bell curve distribution).

Did you know that the majority of growth charts used until recently were collected using the data from artificially fed babies, known to be heavier. Breastfed babies follow a different growth curve: they gain weight faster than the formula-fed in the first 2-3 months and slower afterwards. Breastfed infants remain lighter even AFTER introducing solids.

Both 1977 NCHS and the CDC 2000 growth charts were collected using the data from mostly artificially fed babies. They show higher infant weight and length compared to an average breastfed baby (no difference in head circumference – a surrogate marker for brain development). So a breastfeeding mum goes to her doctor or a nurse for a baby check. While sitting in the waiting room she looks at other babies and compares her own bub’s lean frame to the plump cheeks and fat rolls. The length and weight measurements are taken and shock! horror! the baby is below the 50th centile! The anxious mother then endures a well-meaning interrogation: has your baby been sick recently? is she spending enough time on the breast? are you feeding her when she is hungry or do you ignore the crying? do you smoke, drink alcohol or inject heroin? The anxiety levels are rising… Do I have enough milk? Maybe my breast are too small/too large/somehow inadequate… Aaaargh!

Here is a breastfed growth pattern (red data points) superimposed onto the CDC 2000 growth chart.

Pretty telling. How often do mothers start supplementing with formula, start solids early or add fruit juice when they think their baby is smaller than “should be”?

 In 2006 the WHO has developed new growth charts based on breastfed babies, effectively declaring their growth pattern as the norm, not an anomaly. You need to check which chart your doctor uses.

Another problem with relying on numbers is that it dumbs people down. When you treat people like sheep, they tend to see themselves as sheep. They trust the authorities to tell them what is right and what is wrong and forget to trust themselves. In a normal world preschools wouldn’t have to contact parents to tell them that their kid is overweight. The society seems to have divided into those who recite with relish the latest child obesity statistics and those who are in denial about the size of their little La-a (pronounced [La"dash"a], no kidding, I met one in a kid’s hospital).

So what if you were on a receiving end of that school nurse phone call? You are duly humiliated. Nobody has to accuse you of being a bad parent, most parents will jump to that conclusion themselves. And then they will go looking for answers.

Does my child eat too much? How do I say “No” to the little monster asking for sweets? What are the good healthy snack options?

And here are some healthy snack ideas from the Australian government-run website HealthyKids:

Low fat muffins
Raisin toast topped with banana or strawberries
Bread with tasty fillings such as baked beans
Home-made pizza using pita bread or muffins
Toasted sandwiches
Rice cakes topped with peanut butter or vegemite

Here is an example of a healthy kid-friendly breakfast from the same website.

Don’t forget that the fat which was helping develop a healthy nervous system turns into a heart killer on their second birthday. So low-fat dairy products please.

Of course, the “sloth” side of the coin gets just as much attention. Thankfully nobody has yet accused babies of being lazy. But older kids have been put on notice.

A helpful calorie calculator for children 2 and over has this definition of a Moderately Active (a grade between Sedentary and Active) child: “lifestyle that includes physical activity equivalent to walking about 1.5 to 3 miles per day at 3 to 4 miles per hour, in addition to the light physical activity associated with typical day-to-day life.” 

If you ever meet a toddler who WALKS please let me know. In my experience, little tykes are missing the in-between stage between conscientious block building and running with abandon. Next time I see a calmly walking toddler, I’ll be sure to tell the lucky mum that she needs to increase the activity level to the equivalent (whatever that means) of  over 3 miles a day. Maybe the child can start doing steady laps around the playground while the other kids are engaging in some healthy active play.

Just a few days ago, the chief medical officer of England announced that children under 5 require 3 hours of exercise daily. I imagine baby step classes. How about baby heart rate monitors to measure their caloric expenditure? Disturbing.

I’m not disputing the fact that kids need to be more active (and I’m not talking about Wii Fit). But we have now increased the adult activity recommendations to 1 hour a day most days. Telling adults to exercise doesn’t seem to be working.

Let’s not transfer our own insecurities to our kids. The ridiculous nature of the calorie-in-calorie-out theory looks absurd when applied to children.