How Your Birth Order Can Affect Your Weight  

In WTF weight-loss news, a new study published in the British Medical Journal found that oldest daughters are more likely to be overweight or obese than their younger sister. Yeah, we're confused, too.

For the study, researchers used the Swedish national birth registry (which records the health information of nearly all Swedish mothers and their fetuses from the first neonatal appointment until the birth of their babies) to get the health data of more than 26,000 Swedish women and their sisters. This gave the study authors access to the women's health records at birth and the time they became pregnant. The women included in the study had their first kids between 1991 and 2009.

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After analyzing the data, researchers found that older sisters typically weighed less than their younger sisters at birth, but they were 29 percent more likely to be overweight and 40 percent more likely to be obese than their little sis by the time they were pregnant with their first child. On the bright side, the older siblings tended to be taller. Go figure.

via GIPHY

As crazy as it sounds, this isn't the first study to claim that being the oldest has this random impact on your waistline. According to the study, similar research on men in Sweden and New Zealand found that the elder sibling was more likely to be heavier than the younger one. Also, smaller studies conducted in India, Italy, and Poland showed that birth order played a role in how much a woman weighed.

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So what the heck is the reason behind this strange correlation? Unfortunately, study authors aren't sure since this experiment was purely observational.

Though the large sample size of the study minimized the variables between the different sets of sisters, which could impact the results, it still had some limitations. For example, the researchers only looked at young adult women from a Swedish population, which means these observations don't necessarily apply to all women.

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The takeaway here is that sometimes factors out of your control can impact your weight, but you don't have to let that stop you from living a healthy lifestyle and getting fit. Check out these 25 reasons you can't lose weight—and how to deal with them.

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