Do you ever get the feeling that science figures out a problem a few years after the fact, but then discovers that their methods for fixing the problem are also hopelessly outdated or just plain wrong, which puts us back another several years and at that point we may as well just give up and have wine with breakfast and hot fudge brownie sundaes for dinner?
We know that Americans are fat. (If you don't believe me, look down - do you have a lap?) We also know that kids are getting fatter, which leads to a whole host of problems that will further tax our already overburdened health care system. Now, it seems as if maybe we're not getting fat as fast as we thought they were - although it could be a statistical aberration - and even if they are, we aren't sure if the diagnostic tools we have are relevant!
I acknowledge that I generalize and overdramatize a bit. But after finally convincing myself to start exercising and incorporate more healthy foods in to my diet, the last thing I need is an excuse to head back to the Ben & Jerry Bliss of my Haagen-Dazs Heaven (aka my freezer). (But take heart, fellow peace-seekers/ice cream-lovers - you need look no further than your local grocer's frozen dairy aisle for B&J's new salute to John Lennon, "Imagine Whirled Peace." Support a good cause and enjoy ice cream on a hot summer day? Sign me up!
But I digress.
The Journal of the American Medical Association published a study today that aimed to estimate the prevalence of three measures of high body mass index (BMI) for age (weight in kg / height in meters squared) and examine recent trends for US children and adolescents (using national data with measured heights and weights).
Using the 2003-2004 and 2005-2006 National Health and Nutrition Examination Survey (NHANES) for 8,165 kids, researchers looked at the prevalence of BMI at or above the 97th, 95th, and 85th percentiles for age based on the sex-specific CDC BMI/growth charts (which split things up by age, sex and racial/ethnic group).
The impetus behind the study shouldn't be a surprise: the prevalence of overweight U.S. children and adolescents increased between 1980 and 2004. The results were a bit of a head scratcher, though.
In 2005-2006, 10.9 percent of kids ages 2-19 were at or above the 97th percentile according to the CDC charts, 15.5 percent were at or above the 95th percentile, and 30.1 percent were at or above the 85th percentile for age. What surprised me is not only were there not any significant trends over the years, but the increase in high BMI that's been happening for decades seems to be slowing.
The increase in the prevalence of high BMI for age among U.S. children that was previously seen in NHANES sets (1988-1994 and 2003-2004) "was not observed between 2003-2004 and 2005-2006," the authors state, even by racial/ethnic group.
Two main problems: one, the CDC BMI-for-age growth charts were constructed from reference children in the 1960s, 1970s and 1980s (and 1990s for those younger than 6). Our eating habits, exercise, stress levels, way of life, medicine, everything - it's all changed so much even in the past five or ten years. Two, the authors note that in practice the measurement of body fat is difficult and there are no well-accepted standards for body fatness in children. Thus, weight adjusted for height is more of an indirect measure.
An editorial by Ebbeling and Ludwig published in the same issue of JAMA notes that despite its widespread use, BMI continues to cause confusion among patients and practitioners. This raises several fundamental questions, the editorial says.
One, Ebbeling and Ludwig say, percentiles were based on data collected at a time when BMI for age remained relatively stable, and excess adiposity was not considered a serious threat to public health. Two, the cutoff points are changing. It used to be at risk of overweight, meaning a BMI greater than or equal to the 85th percentile but lower than the 95th, and overweight, greater than or equal to the 95th percentile. Now a committee suggests ramping up the definitions to overweight and obese, and adding a 99th percentile cutoff.
Third, BMI provides no direct information about body composition or fat distribution, they say, which both comprise major predictors of disease. The authors suggest waist-to-hip ratio may better identify cardiovascular disease risk factors than BMI. Plus, different ethnic groups have different risk across the BMI spectrum. Fourth, factors that may influence cardiovascular risk can be present at BMIs below the 85th percentile.
Finally, do the data "reflect a true plateau or a statistical aberration in an inexorable epidemic?"
With all of the caveats, you'd expect more toned-down media coverage. But the first paragraph of the AP story leaves little hope: "The percentage of American children who are overweight or obese appears to have leveled off after a 25-year increase, according to new figures that offer a glimmer of hope in an otherwise dismal battle." To be fair, the AP story does include some of the warnings presented in the article and editorial.
The news has inspired our fellow English-speakers across the pond: a BBC story noted that "despite the caution, experts are hopeful a similar pattern could materialize in the UK."
My favorite line was from the LA Times: "But some researchers said the answer could be that the epidemic has simply reached a saturation point - children just can't get any fatter."
With words like "peaked" and "plateau" splashed across the headlines, will parents and schools and public health officials and kids heed the words of caution and continue to fight the battle of the bulge, or will we all breathe a sigh of relief and take just one more bite of that Ben & Jerry's pint of Chunky Monkey?