Obesity risk depends on birth year – scientists

Obesity risk depends on birth year – scientists
The more recently you were born, the higher your risk of obesity, a US study into body mass index and the “obesity gene” has shown. Before 1942, environmental factors were not as significant as in later years, when they are believed to be twice as strong.

A multi-institutional research team at Massachusetts General Hospital has found out that environmental factors may outweigh genetic ones, as the risk of obesity that runs even in the same family increases over time.

The scientists studying the FTO gene, or fat mass and obesity-associated protein, as well as body mass index (BMI), introduced a new variable, investigating the factors contributing to obesity – that is, the year of birth.

The study was published online in PNAS Early Edition on Monday.

“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,” lead author James Niels Rosenquist, Harvard Medical School instructor, said in a statement.

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“These results — to our knowledge the first of their kind — suggest that this and perhaps other correlations between gene variants and physical traits may very significantly depending on when individuals were born, even for those born into the same families,” Rosenquist said.

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The researchers used data from participants in the Framingham Offspring Study and their children. It was gathered between 1971 and 2008, with participants aged from 27 to 63 at the beginning of the study.

During this 37-year-long period, participants’ BMI was measured eight times, while the FTO variants they had inherited and when they were born showed that a specific correlation between these two obesity indicators is seen only after 1942.

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“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,” Rosenquist said.

The study didn’t name certain environmental factors that increase the risk of obesity, though outlined the importance of post-World War II contributing features, such as relying on technology and high-calorie food, backed by the lack of physical work.

“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,” Rosenquist said.