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Weight Loss

A Link Between Birth Year and Weight?

We already know that genetic factors have an effect on obesity, but there may be another factor as well: the year a person was born.

A research team, reporting in the Proceedings of the National Academy of Sciences, found that the impact of a variant in what’s known as the FTO gene largely depends on the year of a person’s birth. The gene has been linked to obesity risk.

“Looking at participants in the Framingham Heart Study, we found that the correlation between the best known obesity-associated gene variant and body mass index increased significantly as the year of birth of participants increased,” says Harvard Medical School instructor James Niels Rosenquist of the Massachusetts General Hospital (MGH) Department of Psychiatry, lead author of the report. “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.”

The team analyzed data from participants in the Framingham Offspring Study (which follows the children of participants in the original study) gathered between 1971, when participants ranged in age from 27 to 63, and 2008, according to a news release from Harvard.

The association between an FTO variant and a participant’s body mass index (BMI) was seen to be twice as strong in those born after 1942. The authors said that the decreased amount of physical labor people performed after World War II, as well as the increased amount of high calorie processed foods, could be factors in the association.

“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.”

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