A New Year’s Eve story in the New York Times reported on a new study about a well-studied gene, FTO, which is strongly correlated with the development of obesity. Previous research had established that, on average, one copy of a variant of FTO tended to have an extra 3.5 pounds. Persons with two copies of the gene have an extra 7 pounds, significantly increasing the risk of becoming obese.
The new study, published in the Proceedings of the National Academy of Sciences, indicates that this effect did not exist before World War II. Using the longitudinal data from the Framingham Heart Study the researchers led by James Niels Rosenquist of Massachusetts General Hospital found a “robust” relationship between birth cohort and the genotype-phenotype correlation between the FTO risk allele and Body Mass Index (BMI) with an observed inflection point for those born after 1942. The authors observe that “genetic influences on complex traits like obesity can vary over time, presumably because of global environmental changes that modify allelic penetrance.”