Unhappy Birthday for Obesity? Not Exactly

Obesity headlines this past week have been filled with the revelation that birthdays after 1942 are unhappy birthdays if you’re concerned about the risk of obesity. The headlines go like this:

Your Birth Year Could Influence Your Odds for Obesity
Obesity Linked to Year of Birth
Birth Year Affects Obesity Risk
The Year You Were Born Could Determine If You’ll Be Obese

It’s a wonder that an enterprising headline writer didn’t make a link to wine vintages. But to be fair, a few of them hit the mark:

1942 Is a Turning Point in Obesity Gene Variant
Nature, Nurture, and Time

You see, the real point of a very interesting study published in the Proceedings of the National Academies of Sciences isn’t really about unlucky birthdays. It’s about a turning point after 1942 in the interaction between our genes and our environment.

James Rosenquist and colleagues analyzed the risk of obesity for people with and without the FTO gene that is linked to a substantial risk of obesity. They found that the FTO gene didn’t matter so much for people born before 1942 as it did for people who were born after that.

This lines up very nicely with something we already know. Baby boomers are living with a much greater risk of obesity than their parents. But it tells us a little more. It suggests that something changed in our environment after 1942 that’s activating a genetic susceptibility to obesity. Rosenquist commented:

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. 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.

This is bad news for people who don’t want to think too hard about the complex causes of obesity. For people who want to solve the puzzle, it’s a fascinating clue.

Click here to read more from HealthDay and here to read the study.

Birthday Glow, photograph © Earl / flickr

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