It's time to stop blaming your weight on genetics, but it turns out you can make the case for blaming it on the year you were born.

According to new research from the Obesity Research & Clinical Practice it might be harder for Americans today to lose weight, compared to adults in the 1970s or 1980s.

Researchers at Toronto’s York University analyzed dietary data of 36,400 Americans between 1971 and 2008, and physical activity data of 14,419 people between 1988 and 2006. Then, they compared food intake and physical activity, age, and BMI.

Here’s what they found: The predicted BMI was up about 2.3 kg (about 5 lbs) in 2006, despite the fact that the frequency of physical activity increased 47-120 percent between 1988 and 2006.

“We observe that for a given amount of self-reported food intake, people will be about 10 percent heavier in 2008 than in 1971, and about five percent heavier for a given amount of physical activity level in 1988 than 2006,” Ruth Brown, lead researcher, told York University. “These secular changes may in part explain why we have seen the dramatic rise in obesity.”

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The major takeaway is that there may be other factors, besides diet and physical activity, that could potentially be contributing to the BMI increase over time. In an interview with The Atlantic, Jennifer Kuk, author of another study and professor of kinesiology and health science at York University, offered a few hypotheses:

  1. People are exposed to more chemicals (like pesticides, flame retardants, and substances in food packaging) that might be weight-gain inducing.
  2. We’re taking more drugs. Kuk told The Atlantic the rise of prescription drug use (which has been linked to weight gain) could be a culprit.
  3. Kuk, Brown, and the other authors hypothesized that maybe our microbiomes have changed over time — especially since we eat more meat, which is treated with hormones and antibiotics.

Keep in mind these are merely guesses at this point and a lot more research needs to be done to form a big conclusion. In the meantime, just keep exercising regularly, eating clean, and loving your bod, whatever its size.

Photo Credit: Getty Images

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