Your Love for Fat May Be All in the Genes
by Kelly Hensel
It’s no surprise that the United States’ obesity rate is on the rise. However, you might be shocked to find out that it’s not only the environment—living near fast food vs. healthy food stores—that affects obesity, it is also genetics. As Kathleen Keller, Columbia University, said in her presentation “Genetic influences on fat preferences” our genetics influences our preferences for fat, and therefore our propensity for obesity. Fat appeals to humans because of its palatability (it tastes good), its positive post-ingestive feedback to high energy content, and its rich and creamy mouthfeel. Keller went into depth about two genes that impact taste: CD36 and TAS2R38. As she explained there is a phenotype called reduced fat perception which reduces one’s ability to perceive fat in the diet. Therefore, these “non-tasters” seek higher fat foods to compensate, which has a direct impact on their weight. For example, a non-taster would perceive less creaminess in dairy products and therefore the non-taster would like an increased amount of creaminess in the product.
The structurally-related compounds 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC) are heritable and strongly correlated. According to Keller, the PROP phenotype and PTC genotype affect one’s preferences for fat. For example, PROP non-tasters don’t discriminate between high vs. low-fat salad dressings. They can’t tell the difference between 10% and 40% fat but do tend to like the higher fat dressings better. This is why non-tasters may have higher body weight. “The non-taster genotype and PROP phenotype combine for a double whammy when it comes to obesity,” said Keller. It should be noted that the environment still does affect obesity rates. If a non-taster lives in an unhealthy food environment he/she is at risk to be the most obese.
Keller went on to propose that CD36 plays a key role in coordinating fat preference and selection with metabolism and storage of fat. Unlike TAS2R38, CD36 is a large gene with hundreds of polymorphisms. One variation (Rs1761667) is associated with heightened ratings of perceived creaminess regardless of fat content. Another variation (RS1527483) is associated with ratings of perceived fat content. As Keller explained, genotyping common taste genes may provide helpful insight about taste preferences and obesity risks. “Genetic markers may help the food industry better understand consumer response to new product development,” she concluded.