Junkfood Science: One size children

October 22, 2007

One size children

The results of two long-term studies of childhood obesity programs were published last week. The programs tried all of the prevalent techniques: childhood obesity prevention through intensive school-based education to teach ‘healthy’ eating and avoidance of sodas; and behavioral modification and social-environmental weight management, targeting families, peers and their environment to promote ‘healthy’ eating and physical activity.

Here's what they found.


The first was the Christchurch obesity prevention programme in schools (CHOPPS), which was a randomized control trial launched in 2001. This trial included 644 school children in southwest England, aged 7 to 11, and was popularly called the “ditch the fizz” project. It focused on attempting to teach children about the dangers of carbonated drinks, telling them the sugar was bad for their health and would make them fat. Educators also showed them a tooth left in a jar of citric acid and told them that soda would dissolve their teeth. [This myth is a topic for another day.] This was followed by year-long interventions by teachers, including plays, websites, and games to encourage fewer fizzy drinks.

The control group started out slightly larger (in body mass indexes) than the intervention group, with a higher percentage of girls, and would be expected to gain weight ahead of the boys as they entered puberty. The one year results were published in 2004 and reported no difference in the percentage of weight gained by the intervention or control group. They both gained 4% of their starting weight during that year. [Because the control group was larger to start with, they gained on average 0.4 BMI units more.]

The follow-up results three years after the program began were just published in the British Medical Journal. The researchers had lost one-third of the original cohort, leaving an even greater percentage of boys in the intervention group. Of the remaining 434 children, they found, not unexpectedly, that all of the children had grown. The average BMIs of the control group had increased 1.4 units and the intervention group by 1.1 units, and again, there was no statistical difference in their BMI changes.

Nor were there any statistical differences in the numbers classified as “overweight” or “obese” [current classifications are correctly termed "at risk for overweight" and "overweight"]. As the authors explained, they “analyzed the data for each measure of change from baseline using baseline values, sex, and secondary school as covariates or cofactors. This made no material difference to the significance levels or mean changes between control and intervention group.”

They concluded:

The original project provided hope that a simple intervention could be beneficial in preventing obesity, but our new results show no effect two years after the end of the intervention.

Weight control

The second randomized controlled trial, published in the Journal of the American Medican Association, was led by Denise Wilfley, Ph.D., of the psychiatry department at Washington University School of Medicine in St.Louis, MO. A total of 204 healthy fat children, ages 7 to 12, underwent an intensive 5 month family-based weight loss treatment that included strict calorie restrictions, education on “healthy” foods as classified by the Traffic Light Diet, 90 minutes of at least moderate-intensity exercise every day at least 5 days a week, limits on sedentary activities, and behavioral change training which included a family-based reinforcement system.

The children were then randomized to a 9-month intense “behavioral skills” or a “social facilitation” weight maintenance program or to a control group. The behavioral intervention used a “cognitive-behavioral approach” adapted from adult weight maintenance programs and substance abuse disorders. It emphasized teaching self-control to maintain balances of calorie intakes and physical activity. The social approach used family and peers to reinforce ‘healthy’ eating and physical activity and remove environmental barriers to healthy lifestyles. Parents were guided to encourage children to form friendships and ensure play dates with peers who were healthy role models for ‘healthy eating’ and physical activity. [Stop and think, for a moment, what they were teaching, here.] Both weight maintenance interventions groups were similar in the amount of contact and duration. The children who hadn't lost sufficient weight, or any at all, were encouraged to continue to try and lose during the maintenance programs.

The researchers found that the weight outcomes for the two intervention groups “were not significantly different from each other across any time points” (throughout the trial or 2-year follow-up period). The children in the intervention groups lost more weight during the weight loss and weight maintenance period than the control group, but rebounded all the more quickly during the first year follow-up. The BMI z scores of the growing children in the maintenance intervention groups went from 1.95 at the beginning of the follow-up period to 2.00 after 2 years. The control group went from 2.04 to 2.11. A difference of 0.02 between the groups. No statistical difference.

In the end, weight maintenance interventions showed no effect on changing the rate of children’s BMI growth.

Nor did the weight control interventions result in lower percentages of children classified as ‘overweight.’ At the end of the intervention period, 52.7% of the intervention group had been labeled as ‘overweight,’ and 60.5% were at the 2-year follow-up. This contrasted with the control group which ended the intervention period with 57.9% labeled ‘overweight’ and 64.8% at the 2-year follow-up. You’ll note that slightly more children under the weight maintenance interventions than the controls rebounded into the ‘overweight’ category during the two-year follow-up.

This study didn’t measure the physical or psychological health impacts on the children from any of their interventions, nor did they consider pubertal stages.

Their future

Although both studies found null results, the authors suggested that more intense and continuous interventions might be necessary.

But, of course, doing more of the same won’t work, either. Nor is it surprising that no obesity prevention or weight intervention program to date has been able to demonstrate effectiveness in changing obesity rates among children or teens long-term. That’s because, as we know, the science has shown for decades that the natural diversity of sizes among kids, as in adults, isn’t about what they eat or the exercise they get. Thin kids may eat like horses, while fat kids like birds and it doesn't much change their natural sizes in the end. As a group, fat and thin eat the same. No dietary or activity factor among children explains the differences in their sizes. The studies and multiple expert reviews of the evidence continue to make these conclusions — as reviewed here, here and here — and they continue to be ignored.

More worrisome, studies continue to ignore the physical and psychological costs of these interventions on children.

© 2007 Sandy Szwarc

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