What Does Your Birth Year Have to Do with Obesity?
The Link Between Birth Year and the Risk of Obesity
"The fault, dear Brutus, is not in our stars, but in ourselves." The opinions of palm readers and astrologists aside, the stars in this instance are little more than a coincidental alignment that coordinates with a birth year.
Researchers have found that the association between a particular gene variant and body mass index (BMI), only dates back to World War II. This discovery implies that environmental changes might have influenced the way genes were expressed, while technological leaps began reducing energy expenditure during the 1940s. It was also the period of onset for high-calorie processed foods.
Researchers found a strong correlation between a variant of the FTO gene and BMI from 1942-1945 and beyond. The FTO gene is the fat-mass and obesity-associated gene. No correlation was found prior to 1942.
Prior studies have shown a link between variations in the FTO gene and a tendency toward obesity, but the new study further suggests the gene might be activated by environment and lifestyle.
Since World War II, high calorie foods, fatty foods, and heaping portions of both have had an influence. People have filled out and weighed more than their parents and grandparents did.
For the current work, researchers at Harvard Medical School and Massachusetts General Hospital examined the proposed link between genetic and environmental factors that were thought to contribute to obesity. They analyzed participants' data from the Framingham Heart Study and participants' data from the Framingham Offspring Cohort, which follows the children of participants in the original study. The Framingham Heart Study was undertaken to determine the causes of cardiovascular disease (CVD) and has followed the health of more than 10,000 people from the town of Framingham, Massachusetts for several decades.
Investigators looked at the body mass index, which measures body fat based on height and weight, of parents and children born in different years. About two-thirds of the 5,000+ children born to the study's participants have had their DNA sequenced. This allowed the investigators to identify which families had the genetic variant associated with weight gain.
When each person's BMI was compared to the year they were born, no association was discovered between the FTO gene and those born before 1942. However, after 1942, there was a strong correlation between the gene and obesity.
The findings were reported December 29 in the journal Proceedings of the National Academy of Sciences.
What It Means
Although the study was not able to specifically identify the environmental differences that increase the risk of obesity when combined with FTO variant, the prime suspects are changes in our food sources and the technology that has stunted physical labor.
The results of the study suggest that when a person was born may impact the correlation between gene variants and physical traits - even among those in the same family.
Since the evidence points toward global environmental factors such as food products and workplace activity impacting genetic traits, genetic studies may now have to be interpreted in a different light. New genetic risk factors may now emerge due to different genetic responses to an environment that is constatntly and rapidly changing.
Prior studies on this subject have not accounted for changes that take place over time in a larger environment.
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