The study, published in PloS One, reports that severely overweight mice have an impaired ability to detect sweet tastes due to a reduced number of taste cells that are capable of detecting sweetness.
Led by Dr Kathryn Medler from the University of Buffalo, the team behind the mouse research said their findings suggest that obesity causes fundemental changes in how taste cells on the tongue function - which may, in turn, plan a vital role in appetite and hunger control.
Medler and her team revealed that when compared with slimmer counterparts, the obese mice had fewer taste cells for sweetness, and that the sweet taste receptors they did have reacted very weakly to sweet stimuli.
"Studies have shown that 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," she explained. "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."
"The obese mice have fewer taste cells that respond to sweet stimuli, and they don't respond as well."
The team noted that while it is 'unclear' exactly how these alterations might be related to obesity, previous research has shown that overweight people have stronger desires for both sweet and savoury foods, but may not taste them as well as thinner people.
It is possible, therefore, that a reduction in the ability to detect sweetness in foods may lead the already obese to consume even more food than their lean counterparts in order to get the same 'payoff' in terms of taste perception, said Medler.
The new study compared 25 normal mice to 25 of their littermates who were fed a high-fat diet and became obese.
The researchers measured calcium signalling pathways in the mice in order to assess the animals' response to different tastes. This process involves measuring small changes in calcium in cells that occur when cells "recognise" a certain taste.
Medler and her colleagues reported that taste cells from the obese mice responded more weakly not only to sweetness but, surprisingly, to bitterness as well.
Taste cells from both groups of animals reacted similarly to umami.
"Our findings demonstrate that diet-induced obesity significantly influences peripheral taste receptor cell signals which likely leads to changes in the central taste system and may cause altered taste perception," concluded the team.
Medler suggested that learning more about the connection between taste, appetite and obesity is important because it could lead to new methods for encouraging healthy eating.
"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," she said. "These cells are out on your tongue and are more accessible than cells in other parts of your body, like your brain."
Source: PLoS One
Published online ahead of print, doi: 10.1371/journal.pone.0079403
"Diet-Induced Obesity Reduces the Responsiveness of the Peripheral Taste Receptor Cell"
Authors: Amanda B. Maliphol, Deborah J. Garth, Kathryn F. Medler