Junkfood Science: Another chapter of "bad" foods (not) making kids fat

August 08, 2007

Another chapter of "bad" foods (not) making kids fat

Among efforts to slim down kids or prevent them from becoming fat, one of the most popular tactics is to restrict energy dense foods — those are the “bad” foods high in calories. The thinking is that by filling kids up with low-calorie, low-fat, high fiber foods like fruits and vegetables, they will eat fewer calories and not get as big. This popular belief continues despite volumes of contrary evidence showing that children will naturally grow up to be a range of weights, shapes and sizes unrelated to their diets; and that the focus on “healthy eating,” restricting calories and fats, has harmful effects for growing children, both physically and emotionally.

So, it will come as no surprise that this recent study published in the American Journal of Clinical Nutrition did not receive any attention in the media. Researchers tested to see if young children adjusted how much they ate depending on the calories in the foods. In other words, does letting kids eat high-fat, high-calorie foods mean they’ll consume more calories in their overall diet, or do they compensate and naturally regulate what they eat over time to the amounts of energy their bodies need?

Parents — who’ve tried to get a youngster who isn’t hungry to eat or to not feed a hungry one — could probably have answered that for them. But it seems every group of researchers needs to see it for themselves.

The children in this study — ages 3, 4, 5, and 6 — were part of an ongoing longitudinal study of growth and development at the University of Pennsylvania and The Children’s Hospital of Philadelphia. Every year, the children’s caretakers completed a detailed 3-day food record of everything the children ate and drank, down to pre-weighing all foods and leftovers on electronic food scales provided. Nutritional analyses were then conducted by research nutritionists. The researchers were especially interested to see if the children (labeled “high-risk”) who were genetically predisposed to be larger, based on their mothers’ prepregnancy weights, had been overeating.

They found that the amount of food the children ate each day inversely correlated to the foods’ energy density. There was no difference between the high and low risk kids. In other words, kids eat less food when they eat foods higher in calories and more with foods lower in calories. Their bodies naturally adjust for calories they need, regardless of the energy density of any particular food.

The researchers concluded:

This indicates that across a range of dietary ED [energy density], daily caloric intake did not vary significantly as a function of ED during these years...These findings held true regardless of whether beverages were included or excluded. This is the first longitudinal study to show that children aged 3–6 y also adjust their daily intake under free-living conditions. These findings thus confirm and extend previous research conducted under laboratory conditions.

Rather than admit that they found nothing to indicate that “fattening” foods led to overconsumption of calories or the development of obesity over time, they went on to try and look for signs that the genetically fat-prone children were being overfed. They reanalyzed the data in a computer model, calculating the amount of food they predicted the children should have eaten compared to what they actually ate — giving no indication how they did this, if they recognized energy intakes are naturally balanced over weeks or if they assumed the kids should be regulating their calories at every meal, how they adjusted for the children’s varying stages of growth spurts, how they adjusted for activity levels (given that wasn’t something they even measured), how they determined what the children with the higher BMIs should have eaten, etc.

Admitting this was “a novel approach of residual score analysis,” the researchers attempted to show changes in compensating ability among the high risk children over the four year period.

They applied a statistical adjustment to their computer model, called a Bonferroni correction. Dr. Steve Simon, Ph.D., research biostatistician at Children’s Mercy Hospitals, explains:

A Bonferroni adjustment is used when there are multiple outcome measures, and there is concern about the possibility that the results might be perceived as being a fishing expedition. The Bonferroni comparison using an adjusted alpha level equal to the original alpha level (usually .05) divided by the number of outcome measures.... the Bonferroni correction can cause a substantial loss in the precision of your research findings...Too many studies have an inadequate sample size [there were only 22 “high risk” kids in this study], and the Bonferroni correction will make this problem even worse.

If they excluded the beverages, they were able to show that there was a gradual loss of compensating ability among the high risk children after age 4, indicating “overconsumption” but “this gradual decline in compensation ability was not seen when beverages were included in the analysis. ” Last I heard, beverages have calories, too. In fact, isn’t it those liquid calories being most blamed for making children fat?

The researchers acknowledged that their modeling found that “the risk group and age interaction was not significant, nor was the linear risk group and age interaction.” Another “unique finding of the residual score analysis,” they said, was that when beverages were included there was no longer a statistically significant difference in the compensating abilities when they adjusted for BMI scores. Yet, with no evidence, they went on to suggest that “heavier children may be more likely to exceed their energy needs through consumption of beverages.”

Despite efforts to find a problem, they could actually only conclude: “the results of the present study suggest that children between the ages of 3 and 6 y[ears] have the ability to adjust their daily food intake on the basis of the ED of their diet to maintain a certain daily energy intake.”

What are the chances that this study, and the body of confirming evidence, will finally be recognized and those child obesity initiatives will lighten up? The odds, sadly, aren’t in kids’ favor.

© 2007 Sandy Szwarc

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