The Weird Thing That Helps Prevent Weight Gain

High altitude, low BMI. It's probably not a pairing you've ever considered, but according to a new U.S. military study, living at high altitudes may help fend off weight gain.

Researchers examined the health records and living locations of nearly 100,000 active members of the U.S. Army and Air Force and found that, over a period of seven years, overweight service members were 41 percent less likely to become obese if they were stationed at military facilities located at a high altitude. Whaaaaaaat?

Here's how it works: At higher elevations, you inhale less oxygen per breath. Your body compensates for the decreased O2 by producing more red blood cells, which carry oxygen to your tissues. Previous research suggests the surge in red blood cells may cause your body to churn out more appetite-regulating hormones. The result: You eat less and keep your weight in check.

And while a change of address might not lead to double-digit weight loss all on its own, a 2013 study published in the International Journal of Obesity did find that people living at the lowest altitudes tend to have the highest BMIs.

Is your city's elevation helping—or hurting—your weight-loss efforts? Check your altitude at viewer.nationalmap.gov. According to past studies, living at least 9,843 feet above sea level is best for lowering your obesity risk.

More from Women’s Health:
Do You Live In One of the Fittest Cities In America?
The Simple Thing You Can Do In The Morning To Lose Weight
How to Lose Weight Without Even Trying

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