The finding, from the Institute for Health Metrics and Evaluation at the University of Washington, could have real implications for the U.S. obesity epidemic, the researchers said.
“If people aren’t in touch with their weight and changes in their weight over time, they might not be motivated to lose weight,” the study’s lead author, Catherine Wetmore, said in an institute news release. The study was based on national survey data involving 775,000 American adults from 2008 and 2009
Wetmore’s team note that many adults thought they had actually lost weight when they hadn’t. That’s important to note, Wetmore said, because data that underestimate the growing obesity epidemic could have serious public health consequences.
For example, she said, “if we had relied on the reported data about weight change between 2008 and 2009, we would have undercounted approximately 4.4 million obese adults in the U.S.”
A nutritionist familiar with the findings said she wasn’t surprised.
“I see this in clinic every single day; people think they are a certain weight, and they are totally wrong. There is a disconnect between perception and reality when it comes to weight,” said Karen Congro, nutritionist and director of the Wellness for Life Program at the Brooklyn Hospital Center, New York City.
“When it comes to weight, there is a lot of magical thinking going on,” she said.
In the surveys used in the study, participants were asked about their weight at the time of the survey, as well as how much they weighed one year ago.
The researchers report that, on average, American adults gained weight in 2008. However, even though the average reported weights rose between the two surveys, Americans polled typically thought they had lost weight in the past year.
Since the prevalence of obesity actually increased slightly between 2008 and 2009 (from 26 to 26.5 percent) and the average weight increased by about 1 pound, the researchers concluded that those surveyed were unclear about the change in their weight over the course of the year.