In Robin Dando's lab, several mice chowed down on a specialized diet designed to make them as fat as possible. "I can say the mice are happy. They love this unhealthy diet, and pretty fast they get pretty overweight," says Dando, an assistant professor of food science at Cornell University.
But the mice were not long for this world. Eight weeks after they started their delicious nosh, they were euthanized and their tongues were excised for direct comparison against their skinnier brethren.
Dando's work, which he and his graduate students Andrew Kaufman and Ezen Choo published Tuesday in PLoS Biology, attacks a curious effect of being obese: why people's sense of taste seems to dull as they gain weight. Doctors have known about the phenomenon for the last few years, after reports published in the last decade showed that obese people performed poorly on taste tests compared with normal weight individuals.
But the fundamental question remained: why? "We didn't have a good grip on cause and effect," Dando says. For instance, was it that a habit of eating heavy foods dulled the tongue's sensitivity to flavors? Or did this have something to do with the mere presence of excess body fat?
To find out, Dando looked at the tongues of his fat and normal-weight mice. Under the fatty diet, he found the taste buds were withering. "The obese ones have about 25 percent fewer taste buds," he says. Taste buds are structures on the tongue made up of about 100 cells and, when the mice got fat, Dando says the older cells were dying off more quickly and being replaced with new, young cells more slowly.