The Obese Don't Always Know It

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Some obese individuals don't realize they have a weight problem, a new study finds. That could be an unhealthy attitude as these same people tend not to exercise and have many risk factors for cardiovascular disease.

The study, based on survey data collected in Dallas, found that one in 10 participants — all of whom were classified as obese — were satisfied with their body size and didn't think they needed to lose a few.

"That is a sizeable percentage who don't understand they are overweight and believe they are healthy," said lead researcher Tiffany Powell, a cardiology fellow at the University of Texas Southwestern Medical Center in Dallas.

Either way, obesity packs many negative health effects, including increased risk of heart disease, type 2 diabetes and hypertension.

Powell will present the results today at a meeting for the American Heart Association's Scientific Sessions in Orlando, Fla.

She notes the study results are limited in that they don't show causality between such misperceptions of body size and unhealthy behaviors. 

Sizing up

In the study, Powell and her colleagues focused on 2,056 individuals who were obese and took part in the Dallas Heart Study. They had an average age of about 40.

Participants looked at nine sex-specific figures (outlines of bodies, with the first showing the slimmest figure and increasing up to the ninth and largest) and chose what they thought they looked like and their ideal figure.

Studies on Caucasians have shown a score of 4 is lean, while a 6 indicates a body mass index, or BMI, of 30. (BMI is calculated from a person's weight and height and indicates body fatness and weight categories that may lead to health problems, according to the Centers for Disease Control and Prevention. A score of 30 or above is considered obese; 25 to 29.9 overweight; 18.5 to 24.9 normal; and below 18.5 is considered underweight.)

About 8 percent of the obese participants indicated they thought their body size was smaller than reality. Such individuals, considered to have body-size misperceptions, said they thought their bodies looked like a 4 on the figure scale on average, with an ideal body size of about 5. Other participants were more on target, choosing an average of 6 for current body size and just under a 4 for ideal.

In reality, participants who were unaware they were obese had an average BMI of nearly 35, while the others had a BMI of nearly 37.

Health costs

Those with a misperception of body size believed they were healthy. But 35 percent of them had high blood pressure, 15 percent had high cholesterol, 14 percent had diabetes and 27 percent were current smokers. These numbers are similar to those found for obese individuals who acknowledged they had a weight problem, Powell said.

If both groups of obese participants have health risks, why does it matter whether they know it or not? Isn't ignorance bliss?

"Even though they have the same risk factors right now, we don't know what's going to happen over time," Powell told LiveScience. Her team is currently working on a follow-up study to figure out just that.

Other unhealthy behaviors researchers found include:

  • Participants who didn't think they were obese were less likely to go to a physician, with 44 percent saying they hadn't visited a doctor in the past year, compared with 26 percent of those without body misperceptions saying the same.
  • Among those who had a doctor visit, nearly 40 percent of the people with misperceptions about body size said their doctor mentioned they needed to lose weight. That's compared with about 70 percent of those in the know about their obesity.
  • Obese people who were satisfied with their body size didn't exercise on average, while others who recognized they had a weight problem exercised regularly.

Why obesity is ignored

To explain why obese individuals don’t recognize their weight issues or health problems, Powell suggests perhaps a lack of education on such issues is partly to blame.

"A larger cause may be cultural beliefs and acceptance of obesity as the norm when most around you are obese," Powell said. "I think as obesity becomes more prevalent and people around you are larger you reset what is acceptable."

And that could explain why they found African Americans and Hispanics were significantly more likely than whites to be satisfied with their body size and believe that they did not need to lose weight.

"We're seeing more prevalence in minority populations because obesity is more prevalent in those groups," Powell said. "I think as a society as all of us become larger we reset what we think of as a healthy body size."

Powell suggests both doctors and communities as a whole need to intervene and nudge obese individuals toward a healthier lifestyle.

"We have to tell people regardless of whether they bring it up that they are obese and they need to lose weight, and they need to change their dietary habits and they need to work on physical activity," Powell said.

Jeanna Bryner
Managing editor, Scientific American

Jeanna Bryner is managing editor of Scientific American. Previously she was editor in chief of Live Science and, prior to that, an editor at Scholastic's Science World magazine. Bryner has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species, including the gorgeous Florida Scrub Jay. She also received an ocean sciences journalism fellowship from the Woods Hole Oceanographic Institution. She is a firm believer that science is for everyone and that just about everything can be viewed through the lens of science.