A surprising link to obesity

Childhood ear infections may pave the way for weight gain in adulthood.
By Michael PriceMonitor staff Print version: page 18
They say the best way to a man's heart is through his stomach, but new evidence suggests the best way to his stomach may be through his ears. Research presented at APA's Annual Convention suggests that ear infections in early childhood have a profound effect on obesity later in life. Researchers presented findings that children who suffer from repeated middle-ear infections, or otitis media, are much more likely to be overweight as children and as adults.
The possible link first came to light when in 1993 University of Florida School of Dentistry researcher Linda Bartoshuk, PhD, and her colleagues administered general health questionnaires to 7,000 Americans, looking for correlations between taste perceptions and health.
"An unexpected finding emerged," Bartoshuk said. A history of otitis media was associated with a higher body mass index. Using statistical analysis, she determined that these ear infections weren't just a correlation; they made an independent contribution to being overweight, she said.
In her studies since, she's found that males may be particularly susceptible: Those with a history of otitis media are almost twice as likely to be overweight or obese as men who have no history of the condition.
"This is not a small effect," she said.
How could an ear infection influence someone's weight? Derek Snyder, a Yale University neuroscience graduate student, explained that a damaged nerve might be the culprit. An important taste nerve, the chorda tympani, runs from the tongue up through the middle ear and into the brain. If the middle ear is infected, the nerve can get damaged. The effect is that certain nontaste sensations, like the creaminess of fat, get intensified.
"When we perceive food in the mouth, several nerves are at work," Snyder said. "Each of these nerves carries a distinct array of sensory information."
The chorda tympani is responsible for the taste perception on the front of the tongue. If that nerve becomes damaged, tastes at the back of the tongue actually get enhanced to preserve overall "taste constancy." But other cues that go into our sensory experience of flavor, including texture, smells and chemical sensitivity, are also enhanced.
Snyder and the other presenters think that the tongue's texture detectors pull double duty when the chorda tympani is damaged. These texture detectors latch onto the intensified creamy, fat sensation. The result is that overall taste perception remains the same, but a person's food preferences shift toward fatty and creamy foods.
"Over time, a history of ear infection may contribute to a more energy-dense diet," Snyder said. After a number of years, this can lead to obesity.
Especially susceptible are a subgroup of people known as supertasters, who, Bartoshuk explained, have an abnormally high number of taste buds. These people make up about 25 percent of the world population.
"These people live in a neon taste world," Bartoshuk said. For them, damage to the chorda tympani might pose an even bigger danger, as their enhanced taste perceptions would amplify the effects.