Americans have generally gotten wider and flabbier over the past few decades, as obesity rates continue to climb. But at the same time, the media bombard us with images of people who seem impossibly thin or muscular. The gap between reality and expectations can leave many people feeling inadequate.

It’s normal to look in the mirror occasionally and wish for a firmer body or more glamorous hair. But some people find they can’t stop thinking about body flaws they believe they have. They may avoid going out with friends or even stop going to work because they feel ashamed of their skin, hair, weight or other features.

“They say they look ugly, flawed or deformed, but in reality they look fine,” says Dr. Katharine A. Phillips, a psychiatrist at Brown University. “The physical flaws they perceive are things we can’t see at all, or they’re really quite minimal.”

Having a negative body image like this isn’t just an attitude problem. It can take a toll on your mental and physical health. If excessive thoughts about your body cause great distress or interfere with your daily life, you may have a body image disorder, also known as body dysmorphic disorder (BDD).

BDD is a psychiatric condition that affects about 1-2% of the population. It occurs slightly more often in women than in men. “People with BDD frequently think about an imagined defect in their physical appearance. The thoughts are difficult to resist or control,” Phillips says. “On average, these patients report that they think about their perceived appearance flaws for about 3–8 hours a day.”

Because of their imagined flaws, many people with BDD avoid going out in public or shun friends and family. About three-quarters have had major depression, and about 1 in 4 attempt suicide.

Much attention has been paid to how culture and the media can damage women’s feelings about their own bodies. But studies suggest that men and boys can also feel they can’t measure up to the broad-shouldered, narrow-waisted, muscular men they see in ads, cartoons, TV shows, movies and even action figures.

“There’s a climate in American society that rewards muscularity and equates it with masculinity,” says Dr. Harrison Pope, a psychiatrist at Harvard Medical School.

Pope and his colleagues have found a wide gap between what men think of their own bodies and what they believe women prefer. In one study, researchers asked men in the U.S. and Europe to select a body size and shape on a computer that they felt matched their own bodies. Then they selected a body that they thought women would find most attractive. On average, the men expected that women would prefer bodies with about 20 pounds more muscle than the men actually had.

But when the scientists asked women which body shapes they liked most, “the women chose perfectly ordinary male bodies, without any extra muscle,” Pope says. “The men seemed to have a very distorted view of what women wanted.”

A skewed view of how muscular you are may signal a type of BDD called muscle dysmorphia. It’s sometimes found among bodybuilders. People with the disorder become obsessed with being more muscular. “They might look in a mirror and think that they look small and wimpy, even if they are actually large and muscular,” Pope says. Their poor body image puts them at risk for illegal use of anabolic steroids and other drugs to gain muscle mass.