Fruit Loops’s Toucan Sam was right when he gave us the command, “Follow your nose! It always knows!” A recent study published in PLoS One was concluded that people’s sense of smell is able to detect the fat content in foods.

"The human sense of smell is far better at guiding us through our everyday lives than we give it credit for," study senior author and neuroscientist Johan Lundstrom said in a center news release. "That we have the ability to detect and discriminate minute differences in the fat content of our food suggests that this ability must have had considerable evolutionary importance."

Researchers at the Monell Chemical Senses Center in Philadelphia believe that it may be possible to manipulate food products’ odor to make low-fat items more palatable in hopes to reduce dietary fat intake.

To test people’s ability to smell fat, the researchers had the participants smell milk containing three different amounts of fat: 0.125 percent (skimmed), 1.4 percent (semi-skimmed), and 2.7 percent (normal fat milk –although full fat is usually between 3.25 to 3.5 percent). Three different groups of participants were used for the study: normal-weight people in Philadelphia, normal-weight people in the Netherlands, and both normal-weight and overweight people in Philadelphia. 

People were able to detect the different levels of fat in all three groups of participants. This ability did not differ in the two cultures tested, even though people in the Netherlands on average consume more milk on a daily basis than Americans. Also, there was no relation between weight status and the ability to categorize fat content.

Dr. Sanne Boesveldt, lead author of the study and a sensory neuroscientist at the center, said, “We now need to identify the odor molecules that allow people to detect and differentiate levels of fat.”

"Fat molecules typically are not airborne, meaning they are unlikely to be sensed by sniffing food samples," Boesveldt said in the news release. "We will need sophisticated chemical analyses to sniff out the signal.”

Additional Resource:

http://www.monell.org/news/news_releases/humans_use_smell_to_detect_dietary_fat