Obesity may be related to the year a person was born, according to new research from the Massachusetts General Hospital (MGH) Department of Psychiatry.  

The FTO gene is believed to play a significant role in obesity risk, an idea supported by a number of recent independent investigations.

Obesity studies tying the condition to genes traditionally studied subjects within a given age range. Researchers who managed the new study realized grouping together people born in different years in these studies would not account for environmental changes that took place during the intervening time.

The Framingham Offspring Study, which follows children born from subjects who participated in the collection of data from 1971 to 2008, was examined in the new study.

The body-mass index of participants was assessed on eight occasions during the course of the current study, and this information was compared to the variant of FTO present in the subjects. No correlation was found at all between the gene and obesity in people born before 1942. However, the link between obesity risk and FTO doubled in people born that year and later. Even family members raised together, in the same environment, were found to be subject to this relation between genetics and the year in which they were born.

Following the Second World War, lifestyles and diet changed significantly for many American families. These include the consumption of preprocessed foods, rich in calories, as well as a reduction in the amount of physical labor performed by most people, as machines and a multitude of labor-saving devices became available to the general public.

"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," James Niels Rosenquist of the Massachusetts General Hospital, said.

Researchers believe this study reveals a significant impact of the environment on gene variants. This could pose significant challenges to researchers, as they attempt to uncover relationships between genes and physical conditions, as well as disease. Additional future environmental changes could also create unforeseen changes in the genetic code, researchers stated.

More than one-third of all Americans are obese, according the Centers for Disease Control and Prevention (CDC). Excessive weight is often tied to risk of heart disease, stroke, some forms of cancer, and type 2 diabetes.

A possible correlation between obesity risk and the year of a subject's birth was detailed in the journal Proceedings of the National Academy of Sciences (Pnas).