Study Finds Birth Cohort Plays Role in Obesity Risk

Year of birth has a larger impact on obesity than genes alone, according to an analysis of the relationship between body mass index and an obesity-related gene variant.

Year of birth has a larger impact on obesity than genes alone, according to research published in Proceedings of the National Academy of Sciences.

According to an analysis of the participants of the Framingham Heart Study, as the year of birth of the participants increased, so did the correlation between the gene variant associated with obesity and body mass index (BMI).

“These results—to our knowledge the first of their kind—suggest that this and perhaps other correlations between gene variants and physical traits may vary significantly depending on when individuals were born, even for those born into the same families,” Harvard Medical School instructor James Niels Rosenquist, PhD, MD, of the Massachusetts General Hospital department of psychiatry and lead author of the report, said in a statement.

The researchers studied data gathered between 1971, on participants aged 27 to 63 years old, and 2008 in the Framingham Offspring Study. BMI was measured 8 times during the study period and the authors analyzed the relationship between BMI and the FTO variants inherited. They found that the association between the FTO variant and BMI was seen mostly in participants born in later years.

The authors did not identify environmental differences that combine with the gene variant to increase obesity risk, but they did not that increased reliance on technology and the availability of high-calorie processed foods that appeared post World War II were likely contributors.

According to the authors, the finding that global changes in the environment modify genetic risk factors adds a new dimension to gene-by environment interaction research. They added that genotype-phenotype correlations may depend on the historical moment in which investigations are conducted or the time period in which study subjects were born.

“We know that environment plays a huge role in the expression of genes, and the fact that our effect can be seen even among siblings born during different years implies that global environmental factors such as trends in food products and workplace activity, not just those found within families, may impact genetic traits,” says Rosenquist. “Our results underscore the importance of interpreting any genetic studies with a grain of salt and leave open the possibility that new genetic risk factors may be seen in the future due to different genetically driven responses to our ever-changing environment.”