Obesity dulls the sense of taste, according to research that offers new insights into why some people enter a persistent cycle of weight gain.
Researchers found that within eight weeks of becoming obese, mice lost 25% of their taste buds. The findings suggest that weight gain not only changes appetite but may also fundamentally alter the way taste is perceived.
“Obesity is by nature very complex,” said Robin Dando, a food scientist at Cornell University in New York and senior author. “There are a bunch of different factors that contribute to our state of obesity – we think a change to taste is one of those, and one that people don’t tend to consider.”
The findings are the latest to push back against the assumption that people become obese because they love food more than the average person and so find it harder to resist. “I think liking food more may not be what’s going on,” said Dando.
Several converging lines of evidence now suggest the reverse may be true.
Studies of brain activity have found that people with higher body mass index appear to find pleasant tastes relatively less rewarding – as measured by their brain response – and so may need to eat more to obtain the same dopamine kick. Other work has shown that people with dulled taste sensitivity tend to gravitate towards sweeter, fattier foods.
The latest findings suggest obesity does not simply reprogramme taste perception at the psychological level.
In the study, the mice were fed either a normal or a fatty diet. After eight weeks, the mice on the high-fat diet weighed about one third more. The scientists found they also had about 25% fewer taste buds than the lean mice.
Taste buds comprise about 50 to 100 cells of three major types, with different roles in sensing the five primary tastes (salt, sweet, bitter, sour and umami). These cells have a rapid turnover, living an average of just 10 days.
The findings suggest taste buds and their progenitor cells are particularly sensitive to damage from inflammatory chemicals that are raised in obesity, resulting in a rapid decline of the overall number.
The study homed in on one specific inflammatory chemical that is elevated in obesity, called TNF-alpha, which acts as a messenger between the body’s cells. The scientists found that mice that had been engineered to be genetically incapable of making TNF-alpha did not experience any reduction in taste buds, despite gaining weight, suggesting this compound may be the culprit.
The team now plan to assess whether the same process occurs in people. “We’re certainly not identical to mice in our physiology, but our taste buds work pretty similarly, and the same factors related to inflammation we think are responsible for taste loss are elevated when we become obese,” said Dando.
Dando said the findings could help devise new approaches to losing weight, with a greater focus on the influence of taste perception on what people eat.