The taste of fat

When I was a kid, people were thought to detect four different tastes: sweet, salty, bitter and sour. Thanks to the work of Russell Keast and his colleagues, we now know that humans can actually detect six different types of tastes.

It was also once thought that taste buds in distinct regions of the tongue were responsible for those tastes. For example, sweet was supposed to be detected by the tip of the tongue. For some reason, all the experiments my friends and I conducted to see if we only tasted sweet with the tips of our tongues never worked. Of course, we now know those experiments didn’t work because all parts of the tongue can detect all the different tastes. In addition, a fifth taste was discovered called ‘umami’ or ‘savoriness’.

Keast and his team have now added a sixth type of taste to the list. It turns out that people can taste ‘fat’. The researchers tested 31 people to see what their threshold of sensitivity was to a variety of common fats, such as oleic acid. Although most people could detect the taste of fat, there was considerable variability.

The scientists took a second group of 54 volunteers and, as with the first group, screened them for oleic acid sensitivity. This time, they also compiled diet and body mass index (BMI) records for each subject, and asked the subjects to rank how much fat they thought were in custard samples containing either 0, 2, 6 or 10% fat. It turned out that the people who were most sensitive to the taste of fat were best able to correctly rank the custard samples by fat content, and also had the lowest fat intakes and BMI.

In other words, insensitivity to the taste of fat correlated with higher BMI. To be clear, this finding does not necessarily imply causation. People who are less sensitive to the taste of fat may eat more fat to compensate, or people who eat more fat may have become desensitized to the taste of fat. Either way, the finding has interesting implications for the weight loss industry.