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Kids’ waistlines still expanding

April 11, 2012, MedPage Today

If current trends continue, more than one in five American children will be obese in 2020, researchers reported.

An analysis of trends from 1971 to 2008 suggests that the average weight of children is likely to increase by nearly 2 kg by 2020 if nothing changes, according to Claire Wang, MD, ScD, of Columbia University's Mailman School of Public Health in New York City, and colleagues. Wang is also a National Collaborative on Childhood Obesity Research (NCCOR) Envision member.

That would mean about 21 percent of those ages 2 to 19 would be obese, up from 16.9 percent at the end of 2008, Wang and colleagues reported online in the American Journal of Preventive Medicine.

The researchers used data from successive waves of the National Health and Nutrition Examination Surveys, starting in 1971 and ending in 2008, to establish linear trends.

That analysis showed that the average body mass index among children 2 to 19 has risen by 0.55 kg/m2 every decade, while average body weight rose by 1.54 kg every 10 years, Wang and colleagues reported.

Extrapolating from these trends to 2020, the average weight among youth in 2020 would increase by about 1.8 kg from 2007 to 2008 levels.

After controlling for age, sex, and race/ethnicity, the researchers found that rates of obesity among children rose 3.6 percent every decade.

A separate analysis of the most recent period, from 1999 through 2008, found that the trend line has not flattened out, suggesting it makes sense to extrapolate to 2020.

Using that data, Wang and colleagues calculated what changes would be needed to hold the line at 2008 levels, or to reach the overall Healthy People 2010 and Healthy People 2020 goals of 5percent or 14.6 percent obesity prevalence, respectively.

The Healthy People 2020 goals also included age-specifıc prevalence targets -- 9.6 percent among those 2 through 5, 15.7 percent among children 6 through 11, and 16.1 percent among adolescents 12 to 19.

Wang and colleagues calculated the "energy gap" -- the reductions in kcal/person/day -- that would be needed to reach the various targets.

They found:

  • Just to stay at 2008 levels would require an average reduction of 41 kcal/person/day -- 17 for those in the lowest age group, 37 in the middle ages, and 67 for adolescents.
  • To reach the Healthy People 2020 goals would require an extra cut of 23 kcal/person/day -- 5, 40, and 31 for kids 2 to five, 6 to 11, and 12 to 19, respectively.
  • And to reach the more aggressive Healthy People 2010 goals would take an average reduction of 120 kcal/person/day -- 33, 149, and 177 for children 2 to 5, 6 to 11, and 12 to 19, respectively.

The changes in diet and physical activity needed to prevent any single child from becoming obese would vary depending on circumstances, the researchers noted.

The 64-kcal cut needed to reach the 2020 goals -- combining the 41 kcal required to stay at 2008 levels with the additional 23 kcal cut needed -- "may not sound like much individually, but it's quite a consequential number at the population level," Wang said in a statement.

"Children at greatest risk for obesity face an even larger barrier," she said, adding "closing this gap between how many calories young people are consuming and how many they are expending will take substantial, comprehensive efforts."

Among possible actions, the researchers suggested that replacing sugar-sweetened beverages in schools could reduce the energy gap by 12 kcal/day -- as long children didn't consume any extra sugary drinks outside school.

In addition, they argued, a comprehensive physical education program could cut eliminate 19 kcal/day among children 9 to 11 and after-school activity programs for children in kindergarten through fifth grade could cut an additional 25 kcal/day.

The study was supported by the Robert Wood Johnson Foundation and the CDC. The journal said the authors made no financial disclosures.

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