Researchers have identified how obesity dulls the sense of taste, driving people to eat larger quantities of calorie-rich foods to satisfy their cravings.
More than one third of American adults are obese and that number is growing rapidly, creating an urgent need for a better understanding of the disease and how it can be treated.
Obesity has been linked to a reduced taste sensitivity that leads people to seek out foods that are richer in sugar, salt and fat to get the same amount of satisfaction.
Researchers at Cornell University have identified the mechanism behind the dulled sense of taste, revealing a possible new avenue for treatment.
A Cornell University study of rats identified the process by which weight gain decreases taste buds, which in turn dulls the sense of taste and leads people to eat more for the same reward
Previous studies have found that weight gain reduces the number of taste buds on the tongue and that losing the weight reverses the reduction, but it was unclear how or why.
A taste bud is made up of about 50 to 100 cells belonging to one of three groups that each have a different role in sensing the five primary tastes: salt, sweet, bitter, sour, and umami.
The study published Tuesday in the journal PLOS Biology is the first to identify the mechanism underlying the decreased number of taste buds.
‘Taste buds operate not only as sensors of essential nutrients but can also trigger powerful central reward from the consumption of hedonically pleasing food,’ Robin Dando, a lead researcher on the study, said.
‘Obese individuals have been reported to display a weakened sense of taste and thus may be driven to consume more calories to attain such reward,’ he said.
Researchers from Cornell’s department of food science and the department of molecular biology split mice into two groups, one that was fed a normal diet of 14 percent fat and one that was fed a diet of 58 percent fat.
After eight weeks the mice on the high-fat diet weighed 30 percent more, but were found to have 25 percent fewer taste buds than the lean mice.
Taste buds have an average lifespan of 10 days because of a quick turnover process that involves a balanced combination of cell death and generation of new cells.
The researchers found that in obese mice, the rate of cell death increased while there was a decrease in the number of cells responsible for generation.
However, mice that were genetically resistant to becoming obese did not show the same results even when they were fed a high-fat diet, which led the researchers to conclude that they’re a result of the accumulation of fatty tissue rather than just the consumption of fat.
Previous research has shown that fatty tissue produce inflammatory proteins, and in this study the researchers found that the high-fat diet increased the level of one of those proteins called TNF-alpha.
A subset of the mice were genetically resistant to becoming obese and were incapable of making TNF-alpha. When fed the high-fat diet, those mice gained weight but did not have a decrease in taste buds.
The researchers were able to replicate the effects of the high-fat diet on number of taste buds by injecting TNF-alpha into the tongues of the lean mice.
Overall the findings suggest that chronic exposure to a high fat diet leading to excess fatty tissue is linked to inflammation that interferes with the balancing system in taste bud turnover.
‘Our results validate a role for taste in the genesis of obesity and suggest a novel direction in the treatment of obesity,’ Dando said.