Just go to a mall, movie theater or other place where teens hang out and you’ll see how the problem of adolescent obesity has gotten so, well, huge. In the past three decades, the obesity rate among adolescents has tripled, and now nearly 18% of Americans ages 12 to 19 are obese. The possible health consequences (high blood pressure, high blood sugar, high cholesterol) may be minimized if kids lose weight. But a new study reveals a disturbing problem linked to teenage obesity that most likely will not go away—hearing loss.

Here’s why a youngster you love may be at risk for having his world go increasingly silent, even while he’s still in his teens…and what you can do to help.

NOW HEAR THIS

For the new study, nearly 1,500 adolescents underwent complete physical checkups including audiometry, testing that measures both the frequency and intensity of sounds that can be heard.

Frequency, measured in hertz (Hz), describes how low or high a sound is. (A bass drum makes a low-frequency sound…a chirping bird makes a high-frequency sound.) The normal human hearing range is from 20 Hz to 20,000 Hz, with the upper range typically diminishing as we pass through adulthood and into old age.

Intensity, measured in decibels (dB), describes how soft or loud a sound is. A whisper is around 25 dB…normal conversation is around 60 dB…a blow-dryer or kitchen blender is about 90 dB…and a jackhammer is about 130 dB.

Disturbing results: Compared with adolescents of normal weight, obese adolescents had higher thresholds—meaning poorer hearing—across all frequencies. The biggest disparity was seen in the prevalence of unilateral (one-sided) hearing loss in the low-frequency range, in which obese kids’ risk for hearing loss was nearly double that of their normal-weight peers—with 15.2% of obese participants affected, compared with 8.3% of normal-weight teens.

The results held even after researchers adjusted for other hearing-loss risk factors, such as current medical conditions, medication use and exposure to cigarettes or loud noises.

HEARING-HARM HYPOTHESES

This is the first time that a study has been conducted to evaluate the relationship between hearing and obesity in adolescents, but studies in adults have already shown that increased weight is associated with low-frequency hearing loss. Because it’s the same low-frequency hearing that is most at jeopardy in both adolescents and adults, the researchers suggest that the “incredibly worrisome” unilateral hearing loss in adolescents found in this study represents “a harbinger of an early and possibly ongoing injury to the inner ear that will progress”—perhaps to both ears—as an obese teen becomes an obese adult.

Possible causes: Obesity may directly lead to hearing loss by means of obesity-induced inflammation, given that fat cells secret inflammatory proteins that may damage the inner ear. Obesity also may indirectly contribute to hearing loss because of the other chronic health problems that excess weight can lead to, such as type 2 diabetes, cardiovascular disease and high cholesterol—all of which have been previously associated with hearing loss.

Listen up: About 80% of teens with hearing loss are unaware that their hearing has diminished. It is vital for obese teens to have periodic hearing tests so they can receive appropriate treatment as needed, the researchers noted—because even mild hearing loss can have negative academic, cognitive, social and/or behavioral consequences.

It’s also important for seriously overweight teens (and their parents) to talk with their doctors about weight-loss strategies. Although hearing loss that has already occurred may not be reversible, it is possible that losing weight may prevent one-sided hearing loss from progressing to the point where it affects both ears.

Reality check: If your teen thinks that hearing loss isn’t a big deal, have him listen to the demos on this Web page from NPR, which give listeners an idea of how incomprehensible speech becomes when a person has serious low-frequency hearing loss or other types of hearing impairments. When it comes to the importance of protecting our ears, the demos are real eye-openers.