Despite obesity rise, US calories trending downward
By Kathryn Doyle
NEW YORK - US adults have been eating steadily fewer calories for almost a decade, despite the continued increase in obesity rates, according to survey data from the Centers for Disease Control and Prevention (CDC).
"It's hard to reconcile what these data show, and what is happening with the prevalence of obesity," co-author Dr. William Dietz, former CDC director of Nutrition, Physical Activity and Obesity, told Reuters Health.
The results, published in the American Journal of Clinical Nutrition, are based on the nine National Health and Nutrition Examination Surveys (NHANES) the CDC has conducted between 1971 and 2010. Several thousand adults aged 20 to 74 were randomly selected every two to four years and asked to recall what they ate over the previous 24 hours.
Dietz and a colleague analysed trends since the 1970s and found that among adults, average daily energy intake rose by a total of 314 calories from 1971 to 2003, then fell by 74 calories between 2003 and 2010.
"Seventy-four calories is a lot, and as I said before, we would expect to see a measurable impact on obesity," said Dietz.
Nevertheless, about 35 per cent of US adult women are obese, and that percentage has held steady since 1999, according to the CDC. For men, obesity has risen from 27 per cent to 35 per cent over the same time period.
Dietz said he would have expected obesity rates to have leveled-off for both sexes and to be decreasing at this point, if people are consuming fewer calories.
The CDC released similar results last month for children: boys have cut their calorie intake by 150, and girls by 80, since 1999. Obesity rates for boys continue to increase, however, while holding steady for girls. (see Reuters story of February 21, 2013 here: reut.rs/15wNN8P).
Experts said it's possible more time is needed to see obesity rates respond to changes in calorie intake. It's also possible that Americans have changed their eating habits but are still not getting enough exercise to burn the calories they do consume. Or, the surveys may simply be wrong.
"If you cut back on calories by 100 calories, you'll plateau 10 pounds lower," but you'll only see about half of that progress over the first year, Dr. Claire Wang, who studies energy intake and expenditure at the Columbia University Mailman School of Public Health in New York, told Reuters Health.