Having a younger sister make you more likely to be overweight - Scientists explain why

May 15th, 2019

Many siblings around the world share a special bond, especially girls. They share clothing, secrets, and a variety of other things throughout their life. Did you know being an older sister also carries the risk of becoming overweight? While hard to believe, a study actually shows this to be true.

Read on to learn more about how your birth order can lead to weight problems later in life.

The Swedish Study

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iser Source: iser

A Swedish study performed over a 20 year period has proven that if you are the oldest of girl siblings in your family that you run the risk of becoming overweight later in life. In the study, 13,406 pairs of sisters, or 26,812 girls, were observed from pregnancy through the first 18 years of life. The results were stunning; the Body Mass Index (BMI) of the older sister was considerably higher than that of the younger sister.

The question is what causes this increase?

Scientific Reason

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ScienceNews for Students Source: ScienceNews for Students

The scientific reasoning for the disparity in weight between older and younger female siblings was simple. According to one theory, older siblings tended to have thinner blood vessels, resulting in a reduction of the nutrient supply to the body. This in turn increased the risk of the body storing more fat, which caused the body to be more insulin resistant later in life, thus causing weight gain.

Cultural Reason

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EverydayFamily Source: EverydayFamily

Another theory looks at the cultural aspects of weight gain. Young mothers are more than likely to overfeed babies that they have earlier in life in an attempt to make sure that they maintain a healthy weight. This results in bad eating habits that follow these individuals throughout their life, resulting in weight gain. By the time the younger siblings are born, the mothers have learned not to do this, resulting in the establishment of better eating habits.

Sibling Rivalry

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Laments of a Loon Source: Laments of a Loon

Sibling rivalry is another theorized cause for increased weight gain in older sisters. This is due in part to the rivalry that siblings often exhibit, namely in the fight for food. Being larger, of course the older sister is going to succeed in these attempts. Another reason linked to sibling rivalry is the fact that young parents tend to spend more money on their older children, leading to an increased caloric intake early on.

Other Impacts of Being Born First

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The Conversation Source: The Conversation

In addition to weight gain, being a first born has some other impacts, both positive and negative. These aspects of being an older sister can follow you through your lifetime. They can even impact your social interactions and can in their own way impact weight gain through depression and other disorders.

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Rob Leveridge Source: Rob Leveridge

Having a younger sister can result in feelings of loss, jealousy, and resentment. First, the older sister feels loss as the younger sister takes over the position she once held as the baby. Next, this loss often results in jealousy as the sister who once got everything has to now sit back and watch her sister get the same treatment. Finally, resentment can build as the older sister’s parents expect her to be more responsible and better behaved than her younger sister.

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lovetoknow Source: lovetoknow

But it’s not all bad. Being an older sister can result in more ambition as they tend to be more achievement-oriented. In addition, older sisters tend to be natural leaders, with many world leaders older siblings. Maybe this is because they are used to leading their younger siblings and keeping them out of trouble.

Source: Bright Side