From The New York Times:
Obesity rates in women have leveled off and stayed steady since 1999, long enough for researchers to say the plateau appears to be real. And, they say, there are hints that the rates may be leveling off for men, too.
The researchers’ report, published online at cdc.gov/nchs, used data from its periodic national surveys that record heights and weights of a representative sample of Americans. Those surveys, said Cynthia L. Ogden, an epidemiologist at the National Center for Health Statistics and the lead author of the new report, are the only national ones that provide such data.
Dr. Ogden added that the trend for women was “great news.� Obesity rates have held at about 35 percent since 1999, convincing her that the tide had changed. “I’m optimistic that it really is leveling off,� she said.
Men’s rates increased until 2003, when they hit 33 percent and stayed there through 2005-6. Dr. Ogden said she would like to see a few more years of data before declaring that men’s rates had stopped increasing.
Here are some takes on the story suggested by Paul Ernsberger of Case Western . (Any mistakes here are probably my fault, not his.)
1) There are two government data sources being drawn on here; the frequently-updated Behavioral Risk Factor Surveillance (BRFS) survey, and the less-frequent but more reliable NHANES survey.
Why is NHANES better? First of all, because the BRFS is a phone survey, it relies on people’s self-descriptions to get height and weight data; but self-descriptions can be mistaken or dishonest. NHANES measures and weighs its subjects to get the data, which is expensive, but more accurate.
Second of all, although both surveys attempt to measure a representative sample of Americans, BRFS excludes people without phones and people who just have cell phones, making it less representative.
Why does this matter? Because the evidence that there are marked increases in obesity (BMI > 30) in every state since 1999 is based on the BRFS; as I understand it, NHANES doesn’t show such an increase. But the BRFS is less reliable.
2) Obesity rates are equal between men and women now, even though statistically weight loss diets and other weight loss methods are used much less by men than by women. Like a lot of other evidence, this suggests that weight loss methods are not successful at reducing obesity rates.
3) A huge number of people will take credit for the plateau in weight. Every purveyor of weight loss advice and programs will claim credit.
4) From the point of view of promoting health, the most important issue is to promote weight stability, and to focus on health indicators other than weight, such as blood pressure and cholesterol.
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