Good News and Bad News in New Childhood Obesity Data

June 04, 2008

by Rochelle Davis, HSC Founding Executive Director

Last week the Journal of the American Medical Association (JAMA) published an important paper about the trends in childhood obesity.  Dr. Katherine Kaufer Christoffel, MD, MPH, the Medical/Research Director for the Consortium to Lower Obesity in Chicago Children (CLOCC) offered this useful analysis of the data:

This week, the Journal of the American Medical Association published an important paper about trends in childhood obesity in the US, entitled, High body mass index for age among US children and adolescents, 2003-2006. The study, by a group at the National Center for Health Statistics led by Cynthia Ogden, PhD, contains some good news, some bad news, and, of course, some questions that remain unanswered. CLOCC members — and others working to combat the childhood obesity epidemic — need to be familiar with all of these.

The good news is that childhood obesity rates have been stable for almost a decade. Analysis of 4 waves of data from the National Health and Nutrition Examination Survey (NHANES 1999-2006) shows that levels of overweight and obesity have been stable during this time for several groups defined by age, sex, and race/ ethnicity.  Thus the rapid rise in rates that occurred between the 1970s and the 1990s has slowed, if not ended. (Earlier analyses, which did not include the latest data, indicated that rates rose through 2003-2004, but this stronger analysis does not support that finding.)

The bad news has at least three parts. First, rates remain high, particularly for the most obese.  This study reports on rates of BMI above the 85th, 95th, and 97th percentiles for age and sex. The NHANES data on children ages 2-19 years allow for 2005-2006 national estimates: 11% above the 97th percentile, 15% above the 95th percentile, and 30% above the 85th percentile. The percentile norms are from years before rising child obesity, so the recent levels are well above historical ones. Further, about 2/3 of those with BMIs above the 95th percentile have BMIs above the 97th percentile, indicating much severe obesity.

Second, disparities remain by age and race/ethnicity.  In general, rates of overweight are higher for older children than for preschoolers, and higher for minorities than for white children. For example: Among Mexican American boys, those above the 97th percentile BMI included 16% of 2-5 year olds, 21% of 6-11 year olds, and 16% of 12-19 year olds. Among 12-19 year olds, those above the 97th percentile BMI included 20% of non-Hispanic black girls, 18% of Mexican American boys, and 9% of white girls.

Third, NHANES is not designed to provide data at the State or City level. Thus we do not know if the national rates reported in this study apply directly to Chicago and Illinois.

By promoting healthy food and physical activity in schools, HSC continues our efforts to combat the health disparities and very high rates of childhood obesity that affect today’s students.