When University of Illinois researchers surveyed over 3,500 college applicants, more than a third couldn't report their weight accurately, and overweight and obese men were more likely to underestimate their weight than women.
"This misperception is important because the first step in dealing with a weight problem is knowing that you have one," said Margarita Teran-Garcia, a U of I professor of food science and human nutrition.
The study is part of the Up Amigos project, a collaboration between scientists at the U of I and the Universidad Autónoma de San Luis Potos in Mexico. In physical exams, the height, weight, and body mass index (BMI) of 3,622 18- to 20-year-old applicants to the Mexican university were recorded; the aspiring students also completed surveys in which they reported their weight status.
Among the college-aged men, 33.6 percent were overweight or obese, but only 16.9 percent described themselves as being in those categories. For women, the gap between perception and reality was smaller; 27.8 percent of women were actually overweight or obese, but only 21.2 percent believed that they were.
"Heavier applicants were less likely to report their weight correctly," said Flavia Cristina Drumond Andrade, a researcher involved in the study.
Identifying weight problems at the beginning of adult life has important health consequences, Teran-Garcia said. "If these young people follow the wrong trajectory, continuing to accumulate weight, they are likely to develop heart disease and diabetes. It's much better if they deal straightforwardly with the fact that they're gaining weight while they're young."
Why are the researchers focusing on Latino body image and behaviors? According to Teran-Garcia, Mexico has the highest rates of obesity and diabetes in the world, and Latinos, the fastest-growing immigrant population in the United States, bring their weight problems, cultural behaviors, and perceptions with them.
"It's important to understand these cultural differences and be able to see things from the Latino perspective so we can create successful interventions," she said.
Andrade said that 18- to 20-year-olds are at the perfect age for intervention and education. "In Hispanic culture, young people often become parents in their early to mid-twenties. When women are at healthy weights, they have healthier pregnancies. When a pregnant woman is obese, there are long-term consequences for the baby."
Are same-age U.S. young people more or less likely to have an accurate body image? According to figures released by the Centers for Disease Control and the International Journal of Pediatric Obesity, American teens are even less likely to report their weights correctly.
Very few participants in the Mexican study overestimated their weight, but those who did were most often female, younger, had parents with less education, and watched more television. If a young woman believes she weighs more than she does, she is at risk for developing anorexia or bulimia, the researchers said.
Ideal body image changes with exposure to Western media, they noted. "The curvier female figure once appreciated in Latino culture is being replaced by the ultra-thin ideal promoted by Western advertisers," Teran-Garcia said.
The researchers plan to continue work in identifying genetic predispositions for obesity in the participants, then studying the interaction between those genetic markers and family environment, cultural beliefs, mental and physical health, and whether and how much the students exercise.
"We will be able to follow many of these students for some time. We expect to have an exit interview with at least a third of our study participants when they leave college," Andrade said.
Explore further: Why do some Mexican parents discourage teens' physical activity?
The study appeared in a recent issue of Body Image.