WEDNESDAY, Aug. 1, 2012 (HealthDay News) -- If you've ever stepped on the scales and been shocked at the number you see, you're not alone: A large new study finds that Americans routinely underestimate the amount of extra pounds they pack on.
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.
"We all know on some level that people can be dishonest about their weight," IHME professor Ali Mokdad said in the news release. "But now we know that they can be misreporting annual changes in their weight, to the extent of more than 2 pounds per year among adults over the age of 50, or more than 4 pounds per year among those with diabetes. On average, American adults were off by about a pound, which, over time, can really add up and have a significant health impact."
The researchers noted that women seemed more aware of fluctuations in their weight than men. Younger people were also better at judging fluctuations in their weight compared to older Americans.
The study's authors pointed out that not all participants thought they lost weight. They added that certain groups were more likely to report unintentional weight gain, including people under 40 years of age, smokers, minorities, and people with sedentary lifestyles and/or less-than-ideal diets.
Another nutritionist said Americans underestimate the amount of calories they take in, as well.
"We live in a toxic environment with a plethora of food choices that are high in simple sugars and carbohydrates," said Sharon Zarabi, nutritionist at Lenox Hill Hospital in New York City."The average person usually underestimates their caloric intake due to the fact that our super size portions have become acceptable. Want to grab a 32-ounce soda at the movie theater with you medium-sized popcorn? Right there you just added almost 900 empty calories."
She added that, "many people are in denial about their weight and as obesity rates rise, larger body frames are becoming more socially acceptable. Citizens are taking less personal responsibility and use the excuse of work hours, stress, and food availability as obstacles to managing their health."
Wetmore agreed that Americans have to get more in tune with what they actually weigh.
"It's very popular right now to talk about the underlying environmental causes of obesity, whether it's too much fast food or not enough parks," said Wetmore, who is a former postgraduate fellow at IHME and now a biostatistician at Children's National Medical Center in Washington, D.C. "While we know that the environment definitely plays a role, these results show that we need to do a better job helping people to be aware of what's going on with their own bodies."
The study was published in the August issue of Preventive Medicine.
The U.S. Centers for Disease Control and Prevention provides statistics on adult obesity.