In a world full of mirrors, what I’m about to tell you may be a surprise. But many overweight people do not know they’re obese. They underestimate their weight, according to a study in the journal Body Image.

Researchers documented the height, weight and body mass index of more than 3,500 Mexican undergraduate students. Then they questioned the students about their weights. The reported poundage differed significantly from reality, especially among males.

More than 33 percent of the males were overweight or obese but less than 17 percent characterized themselves as being in either category. And though more than 27 percent of the women were overweight or obese, only 21 percent believed they were. The heavier the student the more likely they were to underestimate their weight.

The study took place in Mexico because that country has the highest rates of obesity and diabetes in the world. But undergrads in the U.S. are even more likely to underestimate their weight, according to the Centers for Disease Control and Prevention. The researchers note that recognizing a weight problem early on is crucial for weight control as people age. Or you can wind up buying a bigger belt every year.

—Christie Nicholson

[The above text is a transcript of this podcast.]