Previously, it's been shown that obesity can cause changes in the brain, leading some people to over eat food high in saturated fat and refined sugar, as well as cause poorer memory. A new study published by researchers at University at Buffalo found a new physiological trait that can become altered as a result of obesity. Their findings suggest that obese mice have particularly less sensible taste buds than their lighter brethren, and react more poorly to sweets suggesting that obese people may need to ingest more sweets than would be required in normal conditions to get the same sensory bang.
Taste may actually be the most complicated sense, as researchers know less about how this sense works than hearing or sight for instance. This may be because taste is strongly connected with emotions, as various stimuli like bitter, sweet or sour elicit various emotional responses: pleasure or displeasure in various degrees. This makes sense from an evolutionary perspective as taste often was the first barrier between us and food that may be unsafe to eat. It also acts as an incentive driver - ever wondered why meat or sweets taste so good? It's because these high energy foods would have been vital for survival not too long ago, and to make things easier the brain developed a pleasure or reward response to eating high fat and sugar foods. Of course, now that we live in a time of abundance there's no need to stack up and eat all the fat you can before a predator reels in from behind, faced with the choice, however, a lot of people fall into the trap of overeating.
The taste of food is picked-up by taste buds, most of which are located on the tongue. A typical adult has between 2,000 and 4,000 taste buds, while each bud has between 10 and 50 sensory cells. These cells form a capsule that is shaped like a flower bud or an orange. At the tip of this capsule there is a pore that works as a fluid-filled funnel. This funnel contains thin, finger-shaped sensory cell extensions, which are called taste hairs. Proteins on the surface bind chemicals to the cell for tasting. The actual sense of taste itself is relayed to the nervous system through several cranial nerves.
The researchers compared 25 mice obese mice that were fed a high-fat diet to 25 normal weighing mice. To measure how each animal responded to various taste stimuli, the researchers looked at the calcium signaling process that occurs in taste cells. For each kind of "taste" there's a certain calcium level associated to it which can be measured. The researchers found that in obese mice there were significantly fewer taste cells that responded to sweet stimuli, and as if this wasn't enough it was also found that those that responded had a weaker response than usual.
"Obesity can lead to alterations in the brain, as well as the nerves that control the peripheral taste system, but no one had ever looked at the cells on the tongue that make contact with food," said lead researcher Kathryn Medler. "What we see is that even at this level - at the first step in the taste pathway - the taste receptor cells themselves are affected by obesity."
It was hypothesized before that obese people have a less sensitive taste than thinner people, but this is the first study that has evidence to back this idea up, albeit the research is on mice. Medler and colleagues suspect that this lack of sensitivity might encourage people to over eat just to get the same amount of taste response or pleasure reward, adding further weight to an already vicious cycle.
"If we understand how these taste cells are affected and how we can get these cells back to normal, it could lead to new treatments," Medler concluded. "These cells are out on your tongue and are more accessible than cells in other parts of your body, like your brain."
Findings were documented in a paper published in the journal PLOS ONE.